I think the script relied too much on the "Wrath of Khan" mentality the film tries to capture. I never really saw the TNG crew as "action" heroes like the TOS crew was. It doesn't quite come across the screen right.
Yeah, I think they tried to ape TWOK in a too obvious, and clumsy way.
My main problem with the Nemesis was Shinzon, I think. The actor, Tom Hardy, did a fine job as a young version of Picard and is a good actor, but the character was kind of two dimensional, and just came out of no where. How is someone you met 3 hours ago your "nemesis?" With Khan and Kirk, there was like 16 years of history, and it could be argued that Kirk really did screw Khan over, and Khan's need for vengeance was understandable, if not justified to a point.
With Shinzon, his main beef is he is a clone, living in Picard's shadow? The guy already had a distinguished career as a military leader, and where do you go from conquering the Romulan Star Empire? How is Shinzon living in Picard's shadow at that point?
Instead of having Clone-Of-Picard as the main villain, I think it could have been more interesting if Sela was the main baddie . The last time we saw her was in reunion (the Spock episode) and her failed attempt to invade Vulcan. Presumably, she was disgraced, as this was her second command failure.
I could have seen a scenario where Sela, disgraced by her failures to secure control of Q'onos or conquer Vulcan, as well as hating her human half and irrationally blaming picard for sending her mother Tasha Yar to the Enterprise C, is determined to somehow exact her revenge on Picard. I think that could have been a more powerful motive for revenge than Shinzon's. The only problem with that is I don't know if Denise Crosby would have been capable of being a convincing villain.