The entire Xindi arc should have been six episodes tops, with no time travel episodes.
The Dominion war completely over by the end of the sixth season, include any aftermath and looking back. Season seven new material.
I don’t think you could have convincingly done the Xindi arc in just 6 episodes. They had to earn the resolution. You had to see them pushed to the limit and see the way they changed.
I liked that they did the war over two seasons because they allowed it to breathe. To tell stories they might not have been able to tell if it had all been squeezed together. Stuff like Nog and his PTSD, Kira finding out her mother was Dukat’s consort, etc...