I DID go to post 1, page 1 to check for a cutoff date and didn't see what defined "old" and trust me, the 70s IS old!
Well, I'm from the '70s, so I know just how old it is!
The movies from the '70s are just so much different from what came before. I think films from the '70s are a lot closer to 21st-century film, than they are to the movies being made the previous decade. Not so much in terms of quality or originality or production value, but in terms of the ideas being presented, and the attitudes. Not all of them, of course, but in general.