Rock music, by its very nature and history, is a type of music that is predicated on "shocking the establishment", an idea which goes all the way back to Elvis and Bob Dylan, on through The Who/Hendrix/Stones/Zeppelin/Sex Pistols/Metallica. Rock has even taken to shocking its own "established" parameters, as when punk reacted against the complexity of prog, and grunge reacted to the excesses of hair-metal. Throughout its history, it’s been a vicious cycle of action and reaction. It almost didn't matter that one movement featured complex technical playing or whether it featured simplistic sloppy playing... just as long as it was diametrically opposed to the scene that came before it. Like it or not, rock music has been about “trends”…. always striving to make the next big “splash”. Rock has always had that ego-centric need to maintain its importance in the eyes of the public.
Looking at it from that perspective, rock music just doesn't hold much relevance anymore. There’s no music “establishment” to rebel against, which makes it much harder for a single artist or movement to capture the imagination of the general populace. And part of that comes from the splintering of rock (and the music industry in general) into myriad genres and sub-genres. The way music is now distributed and listened to, people have the ability to zero in on their exact tastes and completely ignore whole genres of popular music altogether. In the old days, there was one top 10 chart. Now, there might be 5-6 top different charts depending on whether you decide to focus on R&B, Pop, Dance, Country, Latin, etc.