I will never understand the hate that movie gets. I fucking love every moment of that film and legit consider it the best one of the TNG movies.
The last time Star Trek was good.
I'm apologetic towards Nemesis because I don't find it as intellectually offensive as Insurrection or anywhere near as boring. First Contact fans will rage, but I put First Contact and Nemesis on about the same level of quality. I consider them both big action movies that approach the level of capeshit in how bombastic their plots are, and they both bend the characters as the plot requires, and both of them have very drawn-out action sequences that, while fairly good on a technical level, are ultimately derivative of other action stuff at the time.
Shinzon is the weak link of the movie though. I certainly agree that more time should have been spent on his background and his buildup. Infact, I would have eliminated the scene where he assassinates the Romulan Senate altogether and had them killed offscreen in an exposition dump, just to give Shinzon more time onscreen. I'd also have revealed him as human before Picard even meets him and change the mystery of "Who is this Shinzon guy?" to "Why is a human leading the Romulans/Remans?". I'm not talking a short intro either, I'm thinking a full 15-20 minutes of the movie devoted to setting up Shinzon, setting up the state of the Romulan Empire, and setting up his plan and why he wants to do it. Then at about the 35 minute mark have him and Picard meet and get into the clone backstory.
While I do like the idea of Shinzon, I would also mess with the clone idea a little. Perhaps there was an imperfection in the cloning technology that caused some latent Romulan features to come through. Something to make him more than just some dude. I'd also focus on making his strengths more like Picard's. Instead of being a warrior, show sequences of him winning battles and pulling political deals just by talking it out with his adversaries. Make him more overtly cunning, more scheming. In the movie itself he comes off as just too brutish and quick to resort to force to solve a situation a keen speaker (like we would expect a Picard clone to be) could solve with words.
Additionally, he just does some fundamentally irrational things, like waiting around on going through with the procedure, leaving Picard tied up in a room with only one guard (if he had a problem seeing Picard die because he felt kindred to him or something, maybe show that more directly), letting B4 roam around on his ship without supervision when he knows Picard has an identical android, and especially mind-raping Troi which blatantly served no purpose and instantly made Picard and the Enterprise turn against him. How pent up do you need to be to go after a middle-aged woman anyway? You mean to tell me he could have his pick of any concubine in the Romulan Empire, probably including humans (Sela was the daughter of a human prisoner after all, I'm sure the Empire has at least some they've captured for various reasons) but he mindfucks a random Starfleet officer at the worst possible time? Come on.
Tom Hardy's performance is excellent though. I have to wonder how the man doesn't go crazy with all of the shittily written roles he keeps getting stuck with. He sells the character pretty well.
Nemesis problem was that they expressly and obviously tried to rip off Wrath of Khan.
Nemesis does, but it feels less like a ripoff and more of a homage to me.
Believe it or not I disagree with this. I don't think that a Star Trek story having a clear badguy who wants power automatically makes them a Khan ripoff. Is that a storytelling cliche in general? Of course it is, but its not like Star Trek literally invented that with Khan. Hell, even having an enemy that wants revenge on the main character is a cliche as old as Greek myth.
Now Star Trek is all about navel gazing.
Its been there from the start. Calling Nu-Trek navel-gazy is kind of giving it too much credit honestly; that assumes that it has anything going on in its head at all.