I like the idea of a time war, as in it could be a cool sci fi concept where time travelers keep trying to undo the work of different time travelers to produce different futures to one side’s satisfaction or another. Problem is, I don’t think ENT was really the show for such a concept to be explored. The Xindi are kinda interesting as a concept I guess? Major early rival of the federation comprised of various species in alignment, but it feels poorly executed.
We see the notion of time cops in Voyager-so a future federation doing time travel shenanigans and shit could be an intriguing show in its own right-if and that is if it was handled by writers capable of translating such a high concept sci fi idea to television in a way that worked.