Look, I only know this from an European perspective and Scandinavian perspective. You know what? It wasn't to be played on national broadcast radio, because they had ships on international waters that sent "piracy radio" akin to todays/or a couple of years backs illegal piracy sites, like pirate bay, Napster and Kazaa a decade or two back. You have simply no idea how "new" pop music where perceived over here back then. And who had preferential right of interpretation of what should be on top lists and what to air on radio. It was just after mid 60s they loosened it up, and this wasn't at all in communist countries. In middle Europe they had Radio Luxembourg sending out to European countries. Mind you, not anyone was commie country. The new music wasn't around when it was brand new. It wasn't anything like that in the US. And when this "new" pop music hit the waves, you bet your *ss that even the Beatles were perceived as shock-rock, like punk did some 10-15 years later.
I know of none of my friends who's dads liked Kinks, Jimi Hendrix, et al. They just thought it was a racket, noise, and no form. And these friends TODAY are showing the same resentment towards todays music. "Pop" music. Even if you don't detect it, "pop" music like Britney Spears, Lady Gaga is really hard rock songs WITHOUT any distorted guitars at all, without anything sounding like barbed wire. If you take "I did it again" and spray it with "Whitesnake" color, and loud dirty and "ugly" guitars, you get "Whitesnake".
You have a cognitvie bias when you're determining pop music from past and present. It was the same with all the Kinks, Merseybeat things, and the Beatles, lets not talks about Rolling Stones, where they first came out, my parents balked at them. Some of my friends where FORBIDDEN to listen to that kind of music by their parents (non christian), even if it was on radio. I have yet to hear anyone prohibit their kids to listen to Bieber these days. Maybe there is? Remember Iran forbid all music when Aytollah kicked in his laws, and allowed only "pastoral" and music geared towards their religion.
I have a cognitive bias too, the songs from the Who, Zeppelin and so on rings a bell but to call Zep "pop" is a stretch. They were on the lists though, at least the Who. The difference is that I acknowledges my bias, and have very much understanding of the kids today feeling the same. They're gonna think the same about futures whatever is pop then, they will just shake their heads, and go "... is this!?!?!" You can't objectively judge whatever is on the lists today.
The only thing that riles me up today, is the final loudness war mastering that occurs on every track, which makes it sound like static. Which is maybe why you get fed up very fast of it, since "everything sonds the same". But it doesn't it just sounds like that. HA! Everything in the smack in the brick wall mastering with no dynamics puts a toll on the listening fatigue of people.
Mind you still, I didn't listen to that much pop music in the 60s and I didn't care. When I got interested in any music, I just went for the music that was totally underground and not showing up on lists. British blues boom, hard rock, and later progressive stuff was my thing. Some barbed wire, ugliness, agressiveness, Then I grew up... ha ha...I couldn't care less about ABBA and stuff.