I think there is a certain knowingness amongst music fans of all persuasions these days about how world-changing or epochal their favourite artists can be -- i.e. not very. Add in the much smaller youth market, the vast amount of competition for that market's leisure spending, and the even vaster expansion of information about different choices for leisure spending, and you have a recipe for micro markets, smaller followings for bands, and a lack of commitment to and "belief" in bands. You're just not going to get very much in the way of big rock stars, of hegemonic bands that everyone pays attention to (like them or not) and which vast numbers of (young) people follow. You're not going to get another Led Zepp or Clash.
What you do get are big bands (among young people) that people don't take that seriously -- for example Green Day (whom I quite like, but which everyone knows is faux punk, not real punk), or the Darkness (faux metal, done with great expertise but just for laffs, whom I like when the joke is done well). On top of them, there are really big bands who tend to have either carried their audiences for 20 years (U2, whom I like very much) or have crossed over to much older audiences (Coldplay, obviously -- I adore them -- or less obviously, Doves, who are my band of the year).
And bubbling underneath are rock innovators who are unlikely to get that much attention -- usually because they foreswear tunes. I guess the key example is Arcade Fire (who so far have done nothing for me).
