The final frontier is not that bad, fight me
I think one thing that's really distracting about it is how BAAAADDDDDD the visual effects are. It is really noticeable that ILM is
NOT in charge with this movie.
Beyond that, I think the premise is not a bad one. In fact, it really connects to TOS and its themes. But I think it's undermined by a few things.
1. The process by which people are converted seems too easy. I know Shatner supposedly based Sybok on televangelists and religious conversion, but I just feel like Kirk's senior staff, people who have shown they would follow Kirk into hell, wouldn't turn on him and Starfleet as easily as they do in the movie.
2. This is a massive event involving three major powers and yet it feels so small. It's like Starfleet is just the Enterprise, the Klingon Empire is just one rogue Bird-of-Prey, and the Romulans don't give a damn to even care.
3. The humor doesn't work. Shatner does well with some of the interactions (like the "row-row-your-boat" scene) but a lot of the "funny" moments just come off as stupid. All of the Enterprise falling apart jokes don't really work. And neither does Scotty bumping his head on pipes and Spock's rocket boots.
With all that being said, I do think it has one of the best scenes of any of the movies. The scenes where Sybok tries to convert McCoy, Spock, and Kirk are really good. I've always thought of it as a really significant aspect of understanding Kirk as a character that he REFUSES to release his pain, and argues that it defines who he is. In the end, the audience is left in the dark as to even what Kirk's pain is, but we do know that he values it.
And I've always been more in the Kirk camp of thinking that "closure" on pain is an illusion. People close on houses, not their emotions.