Well, since most of the radio stations present music strictly as "product," you know, background material between the commercials, perhaps the latest audiences in their 20s now only think of music like that as well. At least when they switch on the "radio." That might account for the alleged decline of interest in rock and singer songwriter material over dance, techno & hip hop, tho' I think I"m oversimplifying quite a bit here. As is the habit of commercial radio playlists.
Maybe there is a lot less attention paid to lyrics that aren't a rap. A lot of contemporary music is like bluegrass to me - fun for awhile, but pretty much all sounds alike, with minor fluctuations in the melody. I don't think this indicates any sort of "pendulum" that will "swing back" to many radio stations playing a mix of styles and tempos, but is a sign of the deeper fracturing between styles, since so many outlets, including Pandora and XM, have squeezed "single genre" formats ever narrower, and trained listeners to go for one thing at a time.
Also seems to be so few outlets for more 'eclectic' presentations that I like at night. Heck, so few people know how to segue different sounds into something that's greater than the sum of its parts anymore. But if we keep looking for it, there's probably a few good ones out there. Suggestions?
I'm listening to Canada's "Espace Musique" on my kitchen FM right now from Victoria, British Columbia (across the water from my Seattle area home), and really getting into a lovely eclectic mix of classical, avant garde, jazz, and standards - the host really knows how to go from a John Tavenver choral work to something etherial by Bjork and later a medium tempo jazz quartet (waiting to hear who it is) and a solo Sufi melody and traditional Spanish guitar. Right up my alley, but nothing's like it on any of Seattle's radio stations. I guess that makes me, too, now a fractured-genre listener, but at least I can occasionally find a music mix I can enjoy on non-comm radio. Or the internet. But for "mainstream" adult adult-contemporary, I'll probably have to search for something I'll enjoy from the BBC online. 'Cuz it' ain't on my American radio, except for sometimes from Canada.