Book specifically said that all time travel mechanisms were outlawed and destroyed after the Temporal Wars. Which seems to mesh with ENT: "Storm Front" and the 31st-century Agent Daniels being involved at the resolution of the Temporal Cold War after the Na'kuhl turned it hot. By the time the Burn happened, whatever timeships had previously been in use by the Federation or others had been wiped out, which is why nobody undid it.
Sure, it's theoretically possible that some timeship from further in the past, or the far future, or some other part of the universe unaffected by the ban, could show up. But it seems clear enough that the reason the writers made a point of declaring time travel defunct in the season premiere was not only to explain why the Burn wasn't undone, but to specifically to say to the audience, "No, we're not going to do a 'Year of Hell' time-travel reset button, and this isn't a how-do-we-get-home story like the Mirror Universe arc. This is the permanent status quo of the show from now on." So I doubt we'll see any such story.