I think part of the thing about TATV is that the powers that be were trying to recon the fact that in the TNG era, Archer and his crew mattered. I also think the story became set in the holodeck to avoid fan grumblings about another Sci-Fi/Star Trek plot device: time travel. I personally don't feel there was anything wrong with trying to wrap up the original run of Star Trek with that episode. I do however feel that having two hours to work with would have given Berman and Braga time to explore the TNG view of Enterprise better.
I never saw it as an episode of Enterprise and kind of almost wished they had slapped the TNG intro on there and I appreciate what they were trying to do. They were trying to give us fans one more episode of TNG on their way out, and the only way it was going to happen was under the Enterprise banner. The fact is (nothing against DS9, Voyager or Enterprise) the pillars that holdup this whole franchise are TOS and TNG, and they were trying to show some respect to that fact with a bigger focus on TNG as that is the show most of the behind the scenes crew (not just Berman) started their Star Trek careers on.
I get why a lot of the fans and many of the Enterprise cast grumbled about the episode, sure. I think however, part of that is due to view point. If you view it for the way I think the intent was, that Demons and Terra Prime are the actual ending of the show Enterprise and TATV is the ending of the Prime Star Trek Universe, it's not so bad.
If it had been up to me, I wish they had been able to make a feature film instead that brought all five captains together, but keeping to what they had to work with, I'd have rather it been:
-A two hour episode
-Set on the Titan instead of the Enterprise-D (maybe even have spent some of the episode not on the holodeck and getting to see the Titan at work?)
-Not had the threat been an alien of the week, but rather a species with more Star Trek weight (i.e. Klingons or Nausicaans or something)
-Not kill Trip off (or if they really had to, make it be bigger like saving the entire Federation signing audience)
-Shown something from the Romulan war
Past that, I really don't have any complaints. I think it had a lot of potential that it was never allowed to achieve.