Rock & Roll morphed into Country some time back and what didn't headed to Pop.
Rock exists in different forms and there are still artists/bands playing all forms of it but it is not mainstream like it once was with Classic Rock, the umbrella for Rock like Fleetwood Mac, Journey, REO and Hard Rock like Van Halen, Alice Cooper and Deep Purple, Art/Prog Rock like Yes, Emerson, Lake and Palmer, Moody Blues, Alan Parsons and Metal with Black Sabbath, Metallica and Avenged Sevenfold.
Like every other form of music, when there is a split as there was when the Beatles broke up, some stayed with their Oldies and some moved onto Country.
Grunge had a huge effect on my generation and forced some to seek other music as was the same with Alternative and Electronic.
Where I was once genre driven and group driven, I became sound driven. If I like it, I like it and don't care what it's called. My tastes are so varied and wide now, I can't define what I am a fan of except maybe all the forms of Electronica: Chill, Techno, House, Trance and Ibiza.
I do not know when in happened, maybe during the changes in my life, but music in any form was no longer about how it sounded but how it felt. I used music as entertainment and now I use it as therapy and I look for melodies to lift me.
I differ so much from people in my own age group, I do not have any friends with close to the same musical tastes whereas, at one time that is what unified us. Most stayed with Oldies, Classic Rock or moved to Country. They were not interested in giving change a chance and they've missed out on some great tunes.
I will say this, Rock will never re-capture what it created in the 70's. Sgt. Pepper and Magical Mystery Tour open the gates to the greatest decade in Rock history. So many talented composers and musicians eyes and ears were opened to the possibilities and they seized the opportunity.