They'd get written up by critics, causing movie people to seek them out, and then as buzz grew everyone started trying to figure out how to see them. People would crowd into smaller theaters they normally didn't attend.
Simar movies are made today, but they don't feel the same in terms of the culture around them. They wind up on a streamer, maybe get memed a bit, and then fade away quickly or get lost in the mess of a less unified cultural moment.
It's the 20th anniversary of Napoleon Dynamite, so that's what everyone is talking about, but I miss the whole milieu.
Stuff like Blair Witch Project, The Full Monty, Beasts of the Southern Wild, Reservoir Dogs, Juno, Big Fat Greek Wedding, Before Sunrise, Lost in Translation, The Spanish Prisoner, etc. I didn't love or even like them all, but I miss that era. Some bigger, some smaller, but they felt less steamrolled by everything else.