Well to put it simply nothing fits anynore. Anyone unfamilar with star trek watching STD , SNW and TOS chronologically from stardate or in story earth year would not see them flow as a natural story or even seem in the same decade. It was poorly done.
Appreciate I'm 2 months late to this message but jumping back into the thread I saw it and it struck a chord with me.
When you say nothing fits - I do understand the visual argument for things not fitting (although I disagree for my personal enjoyment I know it matters more to others) but in terms of tone and the perceived change in behaviours, Federation politics/approach, and even the interspecies relationships I think what has gone on in the real world in just the last 10 years supports such wide ranging changes between, say, the start of Disco through to TOS
I'm not making this a politics thread nor commenting on rights or wrongs as I know that is a TNZ topic but if you had told me in 2015 that the UK would have left the EU for example (essentially isolationism and substantially changing long standing, almost considered to be fixed in stone, relations with the EU) and then due to subsequent changes over that period potentially looking to move back closer I'd have thought it was a different universe.
We've seen across Europe and the US huge and more importantly in the case rapid changes that many would say are unrecognisable from 10 years previous (using 10 years as my marker as you said "even seem in the same decade" so feels a good metric).
You can include the Coronavirus pandemic and the impact of that as an unpredicted event that brought massive change across the world as a good example of near overnight change occurring which just shows how easily it can happen.
Disco starts us off with a flashpoint event that forces the Federation into an aggressive stance due to the outbreak of war - something no one saw coming and which was quickly followed by the Control crisis - fair to say that Control and the impact of it going rogue demonstrated that, in the words of everyone's favourite sweary admiral, the Federation is showing some "fucking hubris" and is chastened by it.
This leads into SNW which starts to show Pike and the crew starting the journey towards a more humble and more exploration focussed Federation that is trying to bring itself back from the darkness (they even set that up in Disco S2 where they say they basically kept the Ent out of the war as Pike and his crew where meant to be the ideal of the Federation and what we as fans hold dear so that even if the worst happened there was someone to rebuild - to paraphrase that other franchise "We are the spark that'll light the fire that'll rebuild the Federation"
We reach TOS and we see a Federation near purely focussed on exploration and discovery - yes there are incongruities of course but something that stands out for me is Kirk's "We're human beings with the blood of a million savage years on our hands, but we can stop it! We can admit that we're killers, but we're not going to kill today. That's all it takes knowing that we're not going to kill today." and the theme of The Enemy Within which shows Kirk needs both sides of himself to be who he is.
If that isn't the product of the last 10 years and shows how the TOS era has learned lessons from what has happened there then I don't know what is.
Until the day the sun finally flames out the arguments over the size of the Fed fleet, knowledge of the Gorn, and the size of the Ent and it's damn windows will continue but looking in a more general sense thematically I feel they actually work well as a development arc
Obviously all opinion and so on but just my two cents