How does it not make sense? What have we heard about the 22nd century before Enterprise? There's more than enough room for more than the romulan war.
Now the temporal cold war was stupid in my opinion but the Suliban and Xindi were perfectly fine. We shouldn't assume that we have seen every species known to the federation by the time DS9 ends, there was always room for Enterprise to invent new ones.
Using that logic, would it have made more sense for TNG as a sequel show to be nothing but references to TOS, revisiting planets, bringing back characters, concepts, species etc. to show what became of them since the 23rd century?
I disagree with your logic.