(Part 2 of 2)
I think, looking at the franchise as a whole, the shift in producers hands has served the fictional universe co-incidentally very well. TOS was the originator, so Gene Roddenberry had a blank canvas to establish what the Galaxy of this fictional universe was, and his Federation was a healthy size, but space was filled with unknowns. The TNG-DS9-Voyager galaxy represented Rick Berman's sensibilities (particularly after Season 2 when he really took over). Borders became known. Institutions were more clearly defined. The galaxy had an unknown border but a much of local space was as defined as modern day Earth is. Risa is Space-Hawaii, not a weird alien world. The Meyer-Bennett movies has the Federation being small (still, and rightly) space being big, and weird. Weird aliens, and a no attention paid to the specifics of "the galaxy". We saw a few starships at a time. There was no great fleets patrolling space. But with Star Trek V was definitely the last hurrah of "big weird space". With Star Trek VI, made deep into the run of TNG, the coming order of the 24th century was already showing up. Enterprise, I think, did an excellent job of making local space big, unknown and dangerous (providing a rationale for the Federation... as Archer repeatedly remarks, he seems to be fighting everyone).
And funny enough, I think Discovery captured the transition pretty well in Seasons 1 and 2. Its unintentional because of creative upheaval and the producer's only general interest about the Berman era, but it works. It's a Federation that is much more cohesive and a galaxy much more known and tamed than the Enterprise era (being 90 years later after all), but not nearly so much as the TNG era.. I think it works well as a modern-day bridge between Enterprise and the Meyer-Bennett movies, in way putting a modern spin on the "galactic sensibilities" of TOS. They should be, after all, the same galaxy. And we'll see how much that is the case in Strange New Worlds.
Looking forward, although Discovery almost never gets into this sort of stuff (instead focusing on forgettable characters), I'd like to find out what Warp drive rates at in the 32nd century. Is Maximum Warp now 9.9999? Because for a 500 light year wide Federation, Warp 9.9 can get them across it in about 60 days. At Warp 9.9999, a ship could cover the 75,000 light years in about 137 days, which I think is a very reasonable number if the 32nd century Federation covers the entire Galaxy.
https://www.st-minutiae.com/resources/warp/index.html
This question is integral to "what is the Federation in the 32nd century". We know it's very loose in the 2160s. It's standardized but still a confederation (as opposed to a federation) in the 2260s. In the 2370s, it's clearly much more of a Federation. It seems so far that the 32nd century Federation is back to being a confederation again... much looser than the 2370s Federation. Season 3 Discovery kind of talked about this a bit, with dilithium drying up and the Federation's spread becoming controversial. Perhaps it truly did spread faster than warp drive could make it feasible to act as a cohesive entity. Even within the real world we see "the tyranny of scale" when it comes to democracies. Representative democracy's challenges, functions, the concerns of it's people, the operations of its government and its interval structure all vary between, say , Denmark (population 5.8 million), France (population 67 million), the United States (population 330 million) and India (population 1.38 billion). India's civil service, for example, is larger and unlike any of the others in that list. The modern United States requires it's Federal structure, interstate highway system and air travel. Denmark's small size and land area mean it's government is excellent at dealing with many types of problems quickly, but has limited resources for others.
The same is likely true of the Federation. The Federation - and thus Starfleet - will necessarily work differently when there are 10 members versus 80 vs 183 vs 350 (which again, seems way too low to me, but "planets" is a bad term to begin with for Federation membership).
Which bring us to the essential question (since it's our gateway into this fictional universe): "what is Starfleet?" There is a whole other thread about this, so I'll just touch on it briefly, but it's essential to understanding the world of the Federation.
Trying to shoehorn what Starfleet is into modern terms makes no sense. It's like trying to liken the modern US Military to the Military of 1800. Yeah they share the name of the organization and the linage, but in almost no sense are they the same. Technically speaking, the modern US Military is a creation of World War II and everything before then is a series of adhoc armies erected around a lean meager skeletons. It's not pedantic or inaccurate to say "the US Military did not fight World War I, the National Army did and some of that went on to form the inter-war military that the World War II military was based around".
To extend the metaphor, what Starfleet is in 2161 vs 2266 vs 2293 vs 2375 vs 3189 is likely something that would naturally change to meet the needs of the Federation over that vast length of time. It's bee said before "is it a military"? It's not. It's nothing we have a direct analogue for, and that's perfectly okay, because neither did America in 1800 have an analogue for the modern US military, or the modern Department of Defense (or most of US government).
I think it's safe to assume that Starfleet in 2161 was what the Rise of the Federation books broke it down as: split into defense, exploration, logistical, scientific and managerial branches for a nascent interstellar alliance. By the 2260s-2280s, it clearly has more of sharper dual role between exploration and security, with a heavier lean on security as the 2270s and 2280s bore on.
The most developed, mature Starfleet that we see is of the 2360s and 2370s of course. And we see lots of strange things to our eyes.
We see uniformed civilians with no ranks or weird ranks (Kosinski).
We see Starfleet running or co-running major scientific institutes across every field of study imaginable. We see Starfleet as front line diplomats, working in tandem with civilian diplomats.
We see Starfleet negotiating trade deals and peace agreements, and facilitating interstellar relations, including the Federation wide communications network.
We see Starfleet running a care center for illicitly Augmented humans.
How can Starfleet be all these things as well as the organization that explores space, charts sectors, makes first contact and shoots up the Borg? It's because Starfleet of the 24th century is a unique creation to meet the needs of a 24th century interstellar state that different from those before and after.
If we want to liken it to anything, I think there is one fitting organizational type: a uniformed civil service. While the United States has six armed military branches (Army, Navy, Air Force, Space Force, Marines, Coast Guard) there are two more non-armed uniformed services - the NOAA corps, the uniformed branch of the National Oceanic and Atmospheric Administration, and the Public Health Service Commissioned Corps, the uniformed branch of the US Public Health Service, part of the Department of Health and Human Services. If anything, Starfleet is most like them, rather than the US Military. Even in 2367, the creation of a "new Federation Battle Fleet" was treated as a novelty by shelby. It likely wasn't earlier in Federation history, and certainly wasn't during the Dominion War, when Starfleet was organized into fleets.
Another modern day analogue, though it is a bit of a legal fiction, is the Japanese Self-Defense Forces, aka the Japanese military. Technically speaking, they're all uniformed civil servants. But these is largely due to Japanese history and constitutional limitations.
Regardless of the closest modern analogue, Starfleet in the 24th century is clearly the provider and maintainer of the principle infrastructure that keeps the United Federation of Planets a consistent entity. It is perhaps this post-Khitomer development (made possible by the end of the Cold War with the Klingons), along with the introduction of the Excelsior class, and then later on replicator technology, that most made the Federation of the 24th century a tighter structured entity than the far looser one of the 23rd. Logically, that would directly figure to the explosive growth of the 24th century Federation too.
So what of 3189? It's been poorly fleshed out, but evidently member planets quit rather easily it seems after the Burn. Galactic integration seems far looser in general in the 32nd century than even the 23rd. United Earth doesn't even rule the entire Solar System... it keeps its few vessels in Earth orbit to defend against planetary threats as if it were the 22nd century all over again. Captain Archer made a comment to that effect, in fact, in Enterprise, when he remarked that the Vulcans have had powerful ships for a long time, but keep them close to home because the galaxy is rough. Well the post-Burn galaxy seems very much a return to that.
Also fascinating: the presence of Planetary Defense Shields, something we almost never (or never) saw outside of dialogue before Discovery. I find the presence of them fascinating because of the historic parallels.
During the time of the Roman Kingdom and early Roman Republic, walled cities were the norm in modern day Italy. Cities would raid cities, and a wall was the best defense. Rome was sacked several times. Over the centuries, the Romans conquered the peninsula, ending that threat. They then moved into modern day France, Spain and the Balkans and Greece and North Africa. The last direct threat of a land attack on Rome itself was Hannibal in the late 2nd century BC. After that, Roman cities started growing outside of their walls. By the time of the late republic and early / mid-Empire walls became limited to mostly frontier towns. Major cities across the Roman Empire were instead defended by a mobile, highly professional Roman Army that interdicted potential threats to security, or were fighting enemies on the far frontier. Rome had no need for walls.
I'm sure you can see where this is going. That Roman Army is Starfleet of the 24th century and beyond, likely deep into the 30th century until the end of the Temporal Wars.
We then get to the Crisis of the Third Century, which throws the empire into upheaval for decades. Barbarian migrations in Northern and century Europe destabilize a long secured region. The borders of the Roman empire start to contract. The enemies of Rome catch up organizationally and technologically to an empire that basically took an 80 year break and fought itself. Rome starts losing battles and soon territory. And what happens? The walls go back up. And those walls would stay up, and lead to ever more elaborate fortifications (including Castles) until cannon and mortar fire made them obsolete in the 16th century.
Planetary Defense Shields showing up in Discovery were perfect because it shows what is needed in a galaxy without Starfleet making sure the local bullies are promptly arrested. They're the walls of a much diminished 32nd century Roman Empire, in a sense.
I'd be interested in learning when those shields go up. Did they go up in the Temporal War period or before? Did a series of events cause confidence to fall in Starfleet's ability to keep the peace because it was stretched to thin? Or are they a product of the Burn period - put up because Starfleet wasn't there anymore. Furthermore, will they stay up, as the Federation is rebuilt? A functional Federation in the decades beyond 3189 should go back to the world of 2375, when a core world like Betazed had antique planetary defense systems because it simply had no need for it.
In a round about way, I think we can then conclude what is the Federation and Starfleet of 3189? In a sens it is the same as the Federation and Starfleet of 2161 - trying to make a bunch of disparate pieces work in a looser affiliation first. Maybe, just maybe, the highly institutionalized Federation that had so explored space that it decided to explore Time by the 28th and 29th century, will return one day. But until then, it's back to the "big, weird, dangerous" space of the TOS movie and Enterprise era.