If by mainstream music you mean the songs that are played on the radio all the time, I think some of them do have catchy tunes. Most of them die off after a while. Sometimes there is a song on the “mainstream” that is quite good or okay, unless you’re a hipster, then you hate everything mainstream. I don’t really think it’s fair to say that any particular style of music is ‘bad’, only that one does not enjoy listening to it. I for one, would not categorize myself as a hipster.
I do enjoy listening to underground or indie music, but I don’t mind having a few mainstream songs on my playlist. I mean it’s music. If you like it you listen to it, and if you don’t, well.. you don’t have to listen to it. My point is, it doesn’t really matter if a song I’m listening to is one that’s on the Top 40s chart, or if it’s a song I randomly discovered on some indie band’s soundcloud. It’s all about taste and what you like. We all have the power to expose ourselves to what we like and get away from what we don’t.