A Dominion TNG movie would've been awesome. The excuse that it 'would've confused viewers' is about as lame and insulting as it gets. Maybe it should have had an opening crawl. It worked for those other 'Star' films...
The ninth
Star Trek film should have been a Picard vs. the Dominion film, set during the Dominion War.
Insurrection leaves the uncomfortable taste that while Sisko and the fleet were off fighting and dying, Picard had a comfortable life far from the front lines.
Would the film have needed an opening crawl? Would pitting Picard against the Jem'Hadar have been confusing?
No. And no.
Do World War II movies try to encompass the
entirety of the war? No. They could have done the equivalent of
Saving Private Ryan with Picard and his crew. Give the audience enough context to get up to speed, show a single mission of the
Enterprise, and end the film on a note that while Picard has won a private victory the enormity of the war goes on.
However. At the time Michael Piller was writing
Insurrection, the idea that the Dominion War would be in its second year on
Deep Space Nine was far from Rick Berman's mind; he wanted it over and done within six episodes of the sixth season. That's why the film feels like a post-war movie, because it was written to
be a post-war movie.