Rock was supposed to be hard, fast, and fun. Not "arty" or bloated like Led Zep, ELP, Yes and other assorted Limeys who nearly ruined the genre until punk came along.
...whatever its creators wanted it to be.
There are no "rules" in rock--that's what made it so dangerous AND pleasurable. It was what someone listening to it SAID it was.
Rock survived the corporate monster but died by suicide, when its creators grew up (or at least aged) and decided they wanted respectibility. The Rock n Roll Museum is its tombstone.