It's been like that since music became a business, we just feel that the quality has gone downhill.
Very true, but the technology has made it easier to market untalented people. In the 1960s the model was 'Find talented people, then decide how to market them'. Now it's 'Decide how you want to market your band, then staff it entirely based on looks'. They would have loved to do that in the 1960s, but they couldn't, because they didn't have modern technology to make somebody with no vocal or musical ability sound good.
The Monkees were a lot like a boy band, and marketed the exact same way. Only they were forced to hire people who sounded okay on their own, so the Monkees came out sounding okay if you ignore the asinine marketing.
Heck, Milli Vanilli got shamed, stripped of their awards and run out of the business for doing stuff that's just assumed now.
I only know who Miley Cyrus is because people complain about her all the time. It's the same with Justin Beiber. I have no idea what any of his music sounds like, but in EVERY YouTube comment section his popularity is being bitched about. If people ignored these two, they'd go away faster.
I know who Miley Cyrus and Justin Bieber are because I used to have a job that had me spending a lot of time in supermarkets and retail stores, where they play that shit on repeat all day.
And because I occasionally watch Saturday Night Live and they wet themselves over those two.
If you don't expose yourself to a lot of other media and your job is far away from retail, you can ignore them, but you do kind of see them everywhere.