Interesting views. My experience of hearing plenty of 60s/70s pros who are now with local bands on the pub/club circuit suggests that either they have vastly improved or, just maybe, they were pretty good back then.
A few weeks ago I saw the Crazy World of Arthur Brown. No sign of any iems for click tracks, in fact the guy runningvthe back projection was synching it live on his phone.
But one track, Space Captives, is historic in being the first commercial track recorded with a drum machine instead of a live drummer. For that one track the drummer was like a human metronome. Worked in context, but didn't have the same groove.
Quantisationnis mainly driven by bands/producers who want to be DJ/dance friendly.