The movie In Time (2011). The premise was interesting but I can't even remember the plot because it was so meh.
I also think Idiocracy could have been better. It had good moments, and that's what most people remember, but the overall cohesiveness falls flat. Great moments, iconic scenes, but could have been a better film.
Came to the comments to say In Time. I always have to remind myself how bad it was, because I really like the concept, so the movie tends to be much better in my head than it actually is as I keep adding things that weren't there.