Would Nemesis had been better without the Remans, with a story that just a straight up conflict between the Federation and Romulan Empire? Besides the latest Star Trek movie, there has never been a Star Trek movie that featured the Romulans as the villains. Nemesis toyed with that but instead introduces the Remans, aliens never seen before or since this movie, as the villains.
It seems like this movie would have had a tighter script if Shinzon wasn't a Picard clone, but was an aggressive Romulan commander who wanted war with the Federation. Shinzon launched a military coup to gain control of the Romulan empire, with the Romulan military building the Scimitar in secret, without the Senate's knowledge. As the Praetor, Shinzon could still pretend to be interested in peace as a prelude to war.
This seems less convoluted then the story we got in Nemesis. It also builds upon the tension we saw between the Romulans and the Federation in TNG.