Classic Horror generally means into the early 1950s. The genre changed a lot after that. So yeah, 70s/80s horror aesthetics were quite different.

Isn't '30s to '50s usually get called the Golden Age, with Classic being until the late '80s?

Huh, that's a new one to me. If some people are using it that way, I need to be careful about using "classic". In my reading, both Classic and Golden Age have been used to mean the era dominated by Universal Studios.