I'm also convinced that tone deafness is a spectrum, not a binary thing, and that a lot of people, perhaps most are at least a little bit tone deaf. Or it's possible that tone deafness is a default trait that can only be changed by being exposed to music.

The inevitable trend in pop music to becoming simpler and simpler and more homogenized to me is a symptom of the de-evolution of people's taste in music (on average) because they are not exposed to more sophisticated music, so they never develop a taste for it.

I think it's probably similar to how spelling and grammar seem to get worse every year, corresponding with the decline of reading actual books. But that may be just because I suffer from terminal Grammar Naziism and my sensitivity to it increases overtime.