I'm not sure if I think there was that much diversity even back then. There are always exceptions, but from a completely general point of view, the different british invasion bands from the 60s f.ex are not that amazingly diverse. Neither are the rock and rollers from the late 40s and 50s.
I don't have a problem appreciating such artists, but I find it hypocritical when people use arguments to explain why they don't like modern pop music when they could just as well criticize the bands they love using the same arguments.
edit :
I think there are legitimate reasons why people may not like pop music. I just don't think they're always obvious to the people who say they don't.
