A few years ago at the bass clarinet festival, there were so many excellent bass clarinet players, I almost couldn't believe it at first. I was amazed really at how many very high level players were there. Almost all of them I've never heard of before, there was no reason to, because what they do wouldn't in any way make me hear them anywhere, and I'm pretty active in hearing bass clarinet players when I can (search for more bass clarinet music, etc.). I'm sure all the players there are no where near everyone, probably a minority of all good players (some that I do know who are excellent weren't there.
Now "incompetent or mediocre" bass clarinetists, I don't know so many. Excluding beginners, students who are stuck on bass, etc. Where do all those mediocre bass clarinetists play? Just curious. Usually when I go to concerts, or just players I know, they are relatively high level players, either solo or in orchestra, chamber music, etc.