Eh...I find all sorts of great rock bands that I like and the size of the venue they're filling means little to me. In fact, if they're playing smaller venues then I'm actually more inclined to go to the show because the tickets are less expensive and the atmosphere is better.
With the ease of the internet music is becoming more and more diverse while people who are looking for particular niches can find more bands within it than ever. If you like power metal then there thousands of bands you can listen to that are all writing the same kind of song. If you like bluesy bar rock then you can find thousands of those too. The same can be said for indie rock, piano rock, pop rock, christian rock, and so on and so on. It bothers me more that I can't find anything that doesn't sound like anything I've heard before but maybe that's just me. I guess non of this really has anything to do with particular bands' success and popularity in a physical sense but there are always people who are going to like the same things as you and I think that should be enough so long as the music is still being made.