There’s a lot more to its being dead than sales and market share. During the rock and roll era there was a general understanding that a young person’s personal identity was tied up with rock music.
The original 50s fad where the latest black music style crossed over to whites was completely teen-centered on the white side. We all know the story about the scared parents and preachers, but precisely because the audience were teens the fad was viewed as disposable by most — see the portrayal of rock fans as mindless but harmless dipshits in The Girl Can’t Help It and Bye Bye Birdie.
But once the Beatles and Stones arrived and really took control of people’s imaginations for several years, the premise was generally accepted that rock and roll was inextricable from being young (and therefore from all the other well-known aspects of youth throughout history, such as hallucinogens, being anti-war, and having long hair — not whatever hair you want, but long hair and only long hair). Old farts STILL go on and on about it.
In the 70s and 80s this continued unabated, but listeners split into tribes. Sure, there was Beatles versus Stones in the 60s, but that was nothing compared with Top 40 versus rockers versus punks while the prog nerds sat in the corner looking superior and wishing a girl would ask them who the best organ player was.
When I was a teenager in the 80s actual music critics were referring not just to Debbie Gibson and shit like that as rock and roll, but also to Run DMC and Whodini. This just didn’t make any sense to me — but it did to lots of people, because to them “rock and roll” meant pop music listened to by young people. And this persists — the Rock and Roll Hall of Fame is packed with soul acts that never would have called themselves that.
Anyway, I see the grunge/alternative boom of the 90s as the last time this system was renewed. The White Stripes are definitely worth mentioning as a real rock and roll band that hit big after all that, and the labels tried to make a movement out of it but it just didn’t happen. And you never heard anyone say, Look at those White Stripes kids over there. It didn’t define a group identity.
These days it seems to me like pop songs (including rock songs) get packaged with movies. The kids and adults all like music and want a certain amount of it, but it’s part of a larger cultural package they buy a few times a year. Which includes video games! And it is already a truism that video games replaced rock and roll for a lot of people over the years, including many who must be adults now.
I think rock music will slosh around with all the other pop music for a long time, and every now and then there will be a new band and a little revival, but it won’t define anything again. And that’s not a tragedy. I have enough to last me a thousand fucking years of rockitude.