Rick has this concept, "low information music", which makes so much sense it's scary even.

He has discussed this factual statistic that the last time a #1 chart hit (in the US) had a change of key was... in 2009. (But incidentally a couple of videos ago he found out that there is ONE song right now in the charts that has it. First one since 2009 anyway)...

In terms of information content, popular music has degenerated orders of magnitude in the last couple of decades, coinciding with the decline of rock music and its almost complete replacement with hip-hop derivatives.