I see the point here. Not all bands, and singers who are popular, "mainstream," or "trendy" are rubbish. . . At least in regards to them being good at what they do (whether or not you like their music).
I think a lot are very talented, and make good music. Alicia Keys, for instance, I'm not really a fan of her music, but recognize she's very talented.
Of course you have plenty who are pure rubbish, and with no real talent. . . But "mainstream" doesn't always mean bad.