How could you tell that the fanbase that Nirvana had, listened to hair metal?

You can't, but when any one group or style has that huge of a following, the industry is going to take notice, and switch gears.

The problem is, there are too many fillers. Too many makeshift bands are out there making thoughtless music.

Exactly. That's my point. You get five Linkon Parks to one.... Shit, I can't even come up with a group that really shines right now. Perhaps CCR? Older stuff, but still good.