I remember reading a science fiction story in the late 70s by Poul Anderson in which an aging capitalist and an aging communist come to blows in a bar in a small town somewhere in the not-very-distant future, arguing about where it all went wrong. Turns out that as soon as solar became really, really cheap, both of their economic models just…went away, along with the belief systems they'd sustained. The younger townspeople don't even really understand what they're arguing about…