I think, by and large, mainstream music has always sucked.... amongst all those
inspirational Dylan's, Beatles, Doors, Stones etc, you still had crap like "Yummy Yummy I've Got Love in my Tummy".... in the 70's with all that great prog, punk and the like, you had the Captain and Tenielle...
In the eighties, amonst all that great early grunge and alternative, you had crud, too... every era's mainstream seems to throw up a mix of utter junk and just a few transcendental, great artists....