I watched the first 4 minutes of the original video and turned it off. You can't compare The Beatles' "A Day In The Life" to Britney Spears, you can't suggest Led Zeppelin, The Beatles, etc, were just "pop". For the argument to be valid, you need to be comparing true like with like, so maybe comparing modern pop with pop singles of the 60's, 70's, 80's, etc. Of course, it is still probably generally getting worse but you still need valid comparisons. There was some dire pop around in the 70's - I recently played a whole Bay City Rollers album - blimey, it was sh*te.

My faith in "modern" music was recently restored by The War on Drugs, but they do have a retro feel

https://www.youtube.com/watch?v=IcxWyfGR-2A

Sounds better via You Tube than many 70's prog rock albums too