I was just having this conversation last night with a few of my girlfriends and one of their sisters was there who is 21. My friends and I were talking about how in middle school we would use the actual physical encyclopedias for research...and even early high school we would just use the Encarta CD ROM...the 21 year old was like "whaaaaaa? I don't even..."
Yeah but they knew who they were.
Also your theory isn't entirely accurate...I've always listening to oldies, classic rock and classic country-- even when I was younger. I listened to new stuff too, but I definitely enjoyed/listened and knew of music from every decade.