Shakaka, you're not exactly wrong, but you aren't right either.
When I say mainstream, I mean something that is aimed to appeal to the masses. These bands are often generic, and only really sound like the next band, which is why I don't listen to common radio. I don't like mainstream because it's so generic; there's only one flavour of music when you listen to mainstream of any genre, and it just gets boring.
That's why I listen to the more obscure yet absolutely brilliant bands that the public isn't really aware of. That, and the older bands. The older bands like Pink Floyd, Led Zeppelin, Queen and so on are all unique, and they can't quite be copied.
Long story short, when I listen to music, I like diversity in what I hear, not the same thing in a different order. That is why I don't like mainstream music. Because a band is popular certainly doesn't mean it's a mainstream band that I don't like though. CoB is one of my favourite bands, for example. They have a MASSIVE fanbase.