Ruby is a beautiful language - Rails is opinionated (much like its creator). If the ways Rails is opinionated works well with your use-case, it's wonderful to use but if not, it's simply horrible.

I don't think RoR usage has declined (maybe as evidenced by the number of "I'm a newb" comments here?) but rather think it's become mainstream so it's simply missing the hype it had when it was the new hipster technology.