Sure, if you read my posts, I am aware dial-twiddlers existed before Sgt Pepper.

But as I noted earlier, Sgt Pepper used backwards-playback, echo chambers, distortion etc---and it was a gigantic commercial hit.

If it had fallen far short of earlier Beatles commercial success, do you think it would have been emulated?

As it was, as both a critical and commercial triumph, it was the starting gun for a stampede of other groups trying to match or better it commercially--and "artistically"--which they thought went hand in hand.   Which was in turn the start of "art-rock".   Sure there were groups which (mostly) fought the tide--which I've also noted earlier.
Stones (mostly)---(they admit Satanic Majesties was a blatant attempt to copy the Beatles)--but afterward went back to straight-ahead rock.

CCR.

Dire Straits.

I've already said what my all-time favorite rock song is--and why. And yes, I'm aware the Who used distortion in "Won't Get Fooled".   But the song worked-- maybe the distortion heightened the rage of the message--hell I don't know. It does help if the song means something--as again in Pink Floyd "Another Brick".

My favorite 60's song--somebody asked. Probably "California Dreamin'". Loved the idea of a song in a minor key extolling California.   And I suppose I'm just a doo-wopper at heart.   California Dreamin' is one you can do totally a cappella--and it's a real kick to do it. Also I loved the flute in it--(which you can whistle).

But there were a hell of a lot of vapid--but pretentious--lyrics after 1966.   Backed up by vapid--and pretentious arrangements.

Before Sgt Pepper the lyrics might possibly be vapid--at least once in a blue moon--well maybe twice. But the arrangements didn't try to assert: "this is art".   That's the difference---and that's what Sgt Pepper inaugurated.

I have nothing against cryptic lyrics. CCR in "Who'll Stop the Rain" is plenty cryptic. But the song is straight-ahead rock. Cryptic lyrics and pretentious arrangements just makes it laughable--and not worth my time.   And again that's what started--in a big way--with Sgt Pepper.

And some rock groups even realized this problem--what do you suppose Dr Hook was aiming at in "Cover of the Rolling Stone"?--another of my nominees for best rock song of all time--a sense of humor in rock is always a huge plus. And a lot rarer than rage.