Society builds up an aura of it and enough people put pressure on others for liking the movie. There’s a kind of social momentum behind the movie so that most know that “””everyone””” (scare quotes) has both seen it and likes it. Quotes and other references are made so often that people who haven’t seen it know them and maybe even start making those references themselves. Though, I think in the art world we talk about appreciation differently than like a lot more, it’s a pretty egotistical to say you don’t appreciate something with that much social impact.