Did anyone watch the video? I'm two minutes in and he's comparing the Beatles, Dylan, Zeppelin and the Kinks to Bieber, Britney Spears and Lady Gaga to make the point that the music of the '60s is better than the music of today. Problem is, there was pop junk on the radio in the '60s too. Record companies were just as shady. Lust for money and wowing the consumer with shiny yet worthless baubles wasn't invented yesterday. Likewise, there's great rock and roll being made today, by innovative bands who are pushing the boundaries.
Some say rock died an early death, but they keep filling up the classic rock airwaves with music. When I was a kid, classic rock stopped in the '70s. Now, it's Pearl Jam. Everything gets old. Some of it ages well and we wax nostalgic for it. The rest becomes Captain and Tennille.
I'd watch the rest but I'm pretty sure I've seen this video before.
He does go into some more scientific metrics to explain the theory, which actually all ring true to me. The generally theme is that the music has gotten simpler in a number of critical metrics, and is less challenging to the listener to digest as there is literally less content there to digest in the first place.