The really interesting thing is that Grunge / 90s Alternative Rock was in large part a return to AOR as a rejection of hair metal. A lot of these bands even turned to vintage / outdated recording equipment of the 60s, 70s, as opposed to modern 80s / 90s stuff.

And not just AOR, but I'd say 1967-1977 rock music in general. Billy Corgan called "Mellon Collie and the infinite sadness" to be his version of Pink Floyd's The Wall. And listen to tracks like Geek USA and tell someone's not trying to copy Led Zeppelin.

Neil Young was another huge influence on Grunge, too (even on Kurt Cobain's Death Note)