That's not the same as stuff magically not being fun anymore. Guns and Roses didn't change, you did.
I reckon it's his thesis that people are supposed to change as they grow older. And I can't argue with that. I mean, never mind Gameboy games and '80s cartoons, which have good claims to "brain rotting" even for kids. If Jackie Paper hadn't ditched Puff the Magic Dragon, it would be serious cause for concern. And adult men playing with tin soldiers was the single biggest sign in the eighteenth and nineteenth centuries that you needed a queen as regent STAT.
(I also thought your thesis was not a literal claim that supernatural media-editing forces weren't a factor, though. So maybe it's best that DJ speak for himself.)