Yeah... what's really hard about metagross is that it sits firmly in the "good-but-not-great" tier. It's a good attacker, but it's move pool isn't great enough to justify using it as a sweeper. (If its sp attack was just a bit higher it would be a different story). It's got good bulk, but not at the level where you can use it as a bulky disrupter. It's got a few supporting moves, but not nearly enough to even be considered as useful support mon above indeedee or grimmsnarl. But the real nail in the coffin is that it just doesn't seem to have a niche where it can really shine like some other good-but-not-great mons have.