Sorry, but manufactured bands have been around for decades. Ever heard of "The Monkees"? They were a rather successful merchandising "boy band" phenomenon of their day.
It helped that, back then, songwriters weren't required to be performers too; many of the "I'm a Believer" is just as much a classic as the "Hey Jude", but has the decency—unlike the latter—not to overstay its welcome.
Have you actually *listened* to some of the Beatles' earlier stuff?
"She loves you, yeah, yeah, yeah
She loves you, yeah, yeah, yeah
She loves you, yeah, yeah, yeah, yeah"
Trite, simplistic, vacuous, unoriginal—the vastly overrated Beatles were all that and more! That guitar combo released an awful lot of forgettable rubbish among those few "classics".
The same can be said for pretty much every artist out there, of both yesteryear and today. Human memories are fickle and selective; we tend to remember the stuff we *want* to remember, but we forget all the crap it was packaged with.
The cliché of music "not being what it used to be" is inevitable: "popular" music is, by definition, deliberately aimed at the broadest possible market, in order to make the most money. Until quite recently, that meant kids. Kids who weren't even a foetus during the Winter of Discontent, or the Vietnam War. Who haven't even learned about the existence of John F. Kennedy, and what happened to him in late 1963. They don't get the references made in songs of that period, so there's a huge market in repackaging the same old clichés of teenage love (see those "She Loves You..." lyrics above), and all the other adolescent preoccupations that seem so insurmountable at that age.
The Baby Boomers skewed the demographics downwards somewhat—kids weren't always quite so important—so feel free to blame them if you wish. And you can also blame them for the Rolling Stones and umpteen other tiresome geriatric acts still being around today.
Every generation has its Elvis, Stones and Who. The originals only have the benefit of being first, but that doesn't make them inherently "better" than those who come after them. There's as much skill and musicianship in a well-mixed, four-to-the-floor dance track as there is in anything Schubert. Mike Oldfield is not inherently better or worse than Tom Petty or Roy Orbison. Or anyone else you care to name. (With the possible exception of most Punk bands.)
There's shit I like, and shit I don't like. Everything is just some bugger else's utterly irrelevant opinion.
Why other people can't adopt the same view escapes me. It's not as if there isn't an "off" switch on most entertainment devices these days.