learn about subjectivism
Learn about taste.
Just browsed through the list of number one albums in the UK since 2005. Of course it includes a lot of shit, but also names like Radiohead, Arctic Monkeys, Gorillaz and Bob Dylan (though I haven't heard that album), all of which happen to be great. And then lots of compilations and not so good albums from great artists of the past, for example David Gilmour and The Prodigy.
Of course you need to have some qualities that appeal to big audiences and there's loads of good music that's never gonna chart, but not all of the music up at number one is shitty or the same.