I would disagree with this. Consider the 50s’ ridiculously simple and banal lyrics, the 60s garage band sound and the same chord progressions over and over (think doo wop), the 70s arguably better with a lot more variety, 80s better with new sounds and expressions, 90s contemporary rock sounds and hiphop, 00s where film music went popular, and the last decade with the indie music boom. Sorry, but todays music is the opposite, better than ever and thriving.