I think it quite fashionably describes the lifestyles of the artists making the music. It is a fact that musicians have different lifestyles than most of society. It is that non-conformist attitude that people love about music and musicians. Since alternative music is now popular and made by megacorporations, it is obviously not the music that is alternative.
Good music is good music.
It is made by good musicians. Bad music is bad music. It is made by bad musicians. Sometimes the results are good. Mostly they are bad.