Stats work fine with a good system. In my experience it helps keep people from vaguely describing things like strength and magic, then doing "asspulls/batmanning" and coming up with things not there.

I used them in a Bleach RP, for things like Zanjutsu, kido, reiatsu, hakuda, shunpo, intelligence, and defense. It kept everyone equal, promoted them when they reached a certain number, and made them intricately different. Meaning they had to use their skills as a whole, during most fights, instead of relying on one(unless, it was something specific)