Would Nemesis had been better without the Remans, with a story that just a straight up conflict between the Federation and Romulan Empire?
Nemesis would have been better if it was better, period. The story itself in outline isn't so bad, none of the cast are any worse than they ever were, and Tom Hardy has since proved himself superb.
They just sort of threw it together, like Insurrection, and it came out a mess. It therefore failed as a film, because it was basically some action set pieces with an attempt at a nature/nurture story tacked on. It also failed as a Trek film, because they expected the last TNG film to be a lot better.
It is actually a perfectly serviceable action film with a great space battle, a very stupid car chase that doesn't work, and some talky stuff between the set pieces that needed re-writes. Trek fans hate it because the last thing they wanted was a serviceable action movie that was thrown together as the last TNG film.
However, even if it had been REALLY good, it probably would not have done that much better at the box office, as it was up against serious sci-fi opposition. I'm a huge trek fan and I was infinitely more excited about LOTR. That is probably why I actually quite like NEM, I never expected it to be much more than it was!