The worst thing that Abrams and his ilk did with AOR was encouraging the pigeonholing of listeners by age and race. The beauty of top 40 radio in the '60s was its diversity. Jimi Hendrix and Frank Sinatra and James Brown and Johnny Cash and the Archies and Ray Stevens and Mary Hopkin and Wilson Pickett and the New Vaudeville Band and Lee Dorsey and Peggy Lee, all on the same station! But when Abrams distilled the old "progressive" format into researched-into-the-ground AOR and threw out all those old R&B and blues records and replaced them with Yes and Emerson, Lake & Palmer because that's what the research told them most of the suburban kids liked most, and the ratings and ad billing jumped, well, it was only a matter of time before top 40 got the same idea.
Sirius XM, of course, is pigeonholed radio taken to an extreme. You're still not going to hear country, MOR, rock and soul on the same channels. Its saving grace is that you can jump from one pigeonhole to another any time you want with your remote. No, it's not 1966 and you're not hearing "Strangers in the Night," "Snoopy Vs. the Red Baron" and "Standing in the Shadows of Love" in the same music set, but that's probably asking too much, as fewer and fewer people remember how radio used to be and the voices calling for the clock to be turned back grow fainter.