I agree with you most of the way, except, in my opinion, your ability to recognize when your moves aren't working and change position is a fundamental skill in BJJ. So what if I can do a kneebar to a dummy standing there with his leg out? It's application in a large range of scenarios that makes you a skilled BJJ guy, not your ability to do moves A, B, and C. Mir is not a top level BJJ black belt in my eyes, he is just a very large one. When faced with an opponent who knows a fair amount of ground, and is larger/more brutish than he, his ground game falls apart. By definition, that's bad Jiu-Jitsu.