> Music is, in the last 15 years, demonstrably homogenising though

This is definitely a trend that isn't unprecedented: the popularity of grunge was in some ways a reaction to the homogeneity of music during the 80s. Rock was a rebellion against pretty much all mainstream music at the time it became popular. Our generation had indie rock. Music is definitely one arena where there are identifiable ebs and flows in terms of creative output and commercial dominance of a particular sound.

I suspect that a similar reaction to the ultra-commercialized nature of FB/instagram/reddit. There certainly seem to be enough dissatisfied people that we may see a 'kill your television' moment for social media in the next few years.