My distaste has nothing to do with the age of the cast. Primarily, I think the movie shits all over Star Trek and what I think it should be about - and what Roddenberry wanted it to be. It completely ruins the characters - especially Spock, which happens to be my favorite character in all of Star Trek. Also, they've reduced Kirk to an arrogant idiot with zero redeeming features, and the less said about their version of Scotty the better.
The fact that the movie has a crappy villain and a beyond stupid plot doesn't help.
Then again, I actually care about Star Trek - because it's one of the very, very few shows that has broken new ground time and time again. It's not just entertainment, and I think I've learned and grown more as a person from the ideas of the show (TOS/TNG in particular) than any other piece of entertainment out there.
I didn't perceive anything that terrible about Nero or the plot. At least not compared to the earlier films. It's certainly not my favorite, but I just don't see it as being that bad.
But let's be honest.. Star Trek has never been about great movies, and some of the older films were laughably bad. For example, Abrams' plot was certainly not worse than that of 'The Voyage Home'.
But then you're obviously far more passionate about Star Trek than I am. I consider myself a fan, but not so much that I've watched every series. In fact, TOS and TNG are the only ones I watched on a regular basis. I've actually seen very little of DS9, Voyager, and Enterprise.
Deep Space 9 is sorta like Babylon 5 - in that it's a big story arc taking place on a space station, but it's quite inferior to Babylon in that way. I'd say it's very good overall, but it can't touch TNG. It's infinitely superior to Voyager and Enterprise, though.
I must admit I don't think I ever watched it beyond the first season, and it sounds like it gets a lot better after that. If I ever have the time to start watching old series' again, maybe I'll give it another chance.