You might have misunderstood me there, I'm neither for nor against this idea. I simply have an opinion on what I think it is. With very rare exceptions, I don't really care what style someone has chosen to use or what they decide to call it. From an entertainment and intellectual level I care about the whole film. (On a personal and professional development level, I lean towards films that are visually potent or particularly well lit, done by a cinematographer I am studying, etc)
But let's be honest, I think their success has less to do with how they made the movie than the
movie they made. Which also touches into your last point, sorta. They are "working in Hollywood." because they made a movie which was a success, met a few people, and repeated said success. They're there on the virtue of their effort and skill, not on the virtue of some nebulous marketing term for the type of movie they made. I think we probably agree on that for the most part; the difference is one of attachment. I haven't latched onto the idea, but I'm just weird like that.
I'll bet there is something to the idea of a knee-jerk reaction to some of the hollow tripe that gets mass marketed and made with massive budgets. Also to the idea that people are tired of going to see a movie knowing some jerk made $20 million to be in it. But I don't think that films which cater to that reaction are the exclusive domain of "mumblecore" either.
I had something for that last sentence of yours, but I'm going to err on the side of "you didn't mean to say that the way it sounded in my head when I read it." Cliff notes: I'm here to talk about a craft that I love - not because I don't get to do it, because I love it.