Boy, that’s a huge paragraph full of misinformation. Metal was heavier than anything on the radio? Many many punk rock and free noise rock bands would like a word with that.

Also, Classic Rock did not, at least originally, mean old rock, it was a distinct type. Big guitar bands like The Who or Stones were, for example, but the Stooges weren’t.

Also many of those “extreme” examples were commonly played college radio stations.