The 1960's, 1970's and 1980's periods were all very creative, with a wide array of new and innovative styles.
In the 1990's it all turned generic, where Britney Spears sounds just like Christina Aguilera sounds just like Jennifer Lopez or whoever.
The main point in the video is that it's cheaper for record producers to selectively market absolute shit like Britney Spears or Justin Bieber as if they're the greatest music ever produced, than to market truly great and innovative talent that may or may not sell, despite their actual talent.
The same trend happened with movies sometime in the early/mid 1990's. It saddened me about a year ago on TCM, when I re-watched the movie Biloxi Blues with Matthew Broderick and Christopher Walken. The editorial comment after the movie said that in the current movie industry, it would be labelled as an independent movie, and not even be given mainstream theatre release. That is how good and innovative work is weeded out, and replaced by absolute garbage.