If you start at 1976, I'd certainly agree a good portion of the pop hits are pretty dire.   The best years were before 1976.

We've been over this before.   For my money the best year for pop music in the rock era was 1966.   In the US charts that year were big hits by the Beatles, Beach Boys, Simon and Garfunkel, Lovin' Spoonful, Supremes, 4 Tops, Temptations, Marvelettes, Miracles, Mamas and Papas, Dionne Warwick, Peter and Gordon, Peter Paul and Mary, etc. All in that one year. And no doubt I've left some out. Even some interesting novelty songs like Winchester Cathedral, and Lovin' You Has Made Me Bananas. And a lot of it was surprisingly mature in any number of ways.   Peter Paul and Mary's offering was in fact mocking some of the others.

There were good songs after 1966, sure, but I'd posit that that the sheer wealth and variety of good stuff peaked in 1966 and began a slow decline. The influence of drugs didn't help--it seemed starting in 1967 that it was awfully easy to snow a drug-addled public with mindless repetition and twisting dials in a studio.

And the 1920's through 1940's were even better than any year in the rock era--probably for the reason I cited.