It takes a while to perfect time travel, as in the 28th Century certain factions can communicate through time but not actually travel through it, while by the 31st Century they've perfected it.
Allegedly. We'll see "later" (in your chronological sequence, earlier in production order) that the technology to travel in time is available as early as the first decade of the 25th century ("Firstborn," "Endgame") and is routine by the 26th ("A Matter of Time"). This is one of the reasons I concluded that Daniels is a big fat liar.
He's too embarrassed to admit that it was the Klingons who made the breakthrough.

Or maybe he's trying to exaggerate the temporal gap between Archer and controlled time travel, to make the whole notion seem so fantastically futuristic, so far away, that Archer is more likely to shrug it off as something beyond his reach. Daniels must be risking a lot by interfering so openly. Best that Archer relate to the whole time travel affair as a distant vision and not something he can place in context as a relatively imminent technological development?
****
Sorry, everyone, that there's not much literature at this point, but that's the situation with Enterprise. By the time we reach TOS there'll be at least as much lit as screen, so bear with me!
"Silent Enemy"
There's a nice balance in this one between the crew easing into their life together out here (Archer charging Hoshi with finding Malcolm's favourite food ready for his birthday) and the sense that space is hostile and the crew aren't ready for it. Archer is forced to confront his motives for being here and begins regretting his decision to launch unprepared, or - more to the point - regretting the pride that drove him to push forward so quickly. He admits that the Klaang issue was more an excuse than anything, that the reason he pushed for the launch was (as we well know) because he thought he had something to prove. He even swallows his remaining pride long enough to call Vulcan for help (not that the call gets through). Space is a lot more dangerous than he realized, and here his sense of responsibility to the crew overpowers his desire to "go boldly".
He orders the ship back to Jupiter for refit. This doesn't sit easily with Trip, who upon hearing Archer suggest that they weren't truly ready asks him "are your ears a little pointier than usual?" T'Pol, though, is rather graceful. When Archer asks her if Vulcans had the same problem with hostile encounters when first entering deep space, T'Pol makes no comment on supposed Human failings and instead simply notes that "it was a different time" because there were far fewer warp-capable species around.
(I wonder why space was so empty when Vulcan made its first long-range spaceflights? I guess the Great Psionic War or other disasters wiped the slate clean. Civilizations that survive from millennia in the past include the Thelasians - a declining, stagnant people whose grip on interstellar trade off toward the future Triborder will be explored in Rosetta, and the Orions, who apparently declined from a true empire into a collection of merchant clans, pirates and raiders, and may have done this several times).
I love the appearance of the "Shroomies", and the entire matter of their mysterious intent. As T'Pol notes, sometimes alien species don't have easily identifiable motives. It's great that we don't unravel that mystery in the episode, never learn what's going on or what the aliens are doing. The crew speculate, but they're pretty shaken by this point (it's good to see them bedraggled and tired, it does legitimately feel like they've been running themselves ragged). This of course allows for all manner of valid explanations. The Rise of the Federation novel A Choice of Futures, which for the purposes of this project is the "official" version, reveals the "Shroomies" - who turn out to be Gamma Vertians - to be far less malicious than assumed, their lack of regard for other species a matter of biological and communications barriers rather than ill intent. Other races don't register as sapient to them. They're cataloguing the potentially dangerous wildlife, basically. Star Trek Online takes a different route and uses them as a genuinely hostile force who, I believe, abduct people to grow additional fungus men - which is an equally valid extrapolation, and better suited for a game, while this continuity's version works better for interesting stories about the Federation's early identity issues. The Shroomies are called Elachi in the STO interpretation. Who knows, though, maybe an offshoot or faction of the Vertians will go rogue some time between the 22nd and 25th Centuries. Perhaps there's room for a version of the Elachi in this continuity after all.
Continuity
Realizing that they're woefully unprepared for the dangers of space, the crew install their experimental phase weapons.
The "Shroomies" - we can call them the Vertians, I suppose - seem to use a rather unique-looking energy weapon that takes the form of crescent-shaped "sheets" that strafe the opponent. Like the Malurians, they have deflector shields.
The Vertian ships are reused as Kovaalan ships in season three, which is apparently coincidence, just how the Xindi-Arboreals are (but aren't actually) using Arkonian destroyers and the Xindi-Insectoids are (but aren't) using repainted Nausicaan raiding ships. Then again, maybe the Kovaalans are the Elachi, that rogue offshoot of Vertians who wound up lost in subspace? Who can say?
I note that this episode apparently takes place prior to Cold Front. Huh. You lied to me, episode order.
Next Time: "Dear Doctor".