Maybe that seems entirely too hyperbolic. Or maybe it seems like an outright lie.
But here's what I mean. I was thinking about how there are a lot of plays out there that are widely read and acclaimed. Shakespeare, Beckett, Williams, et al. But I can't think of any screenplays that literature nerds love to read in their own right.
Maybe that's because movies are so accessible. It's a lot easier to watch Casablanca rather than to track down a performance of Waiting for Godot. And if you actually watch Casablanca, you're going to see the best possible version of it. Going to see some high school do a production of Godot could just make you feel all awkward inside.
On top of that, screenplays are typically written with this purpose, first and foremost: to create a version of the story that everyone on the production team can use as a useful reference. So there's often not a lot of room to get all flowery and poetic when writing a screenplay. If you do, you'll probably just end up frustrating the folks who're trying to figure out what the hell they need to do to make your screenplay a movie. (And on top of that, the general rule with screenplays is that one page is equal to a minute of screen time. Spend too much time trying to add "artistic touches" and your film that would really end up being 90 minutes will appear to be 120 minutes.)
I'm not saying that it's impossible to make a screenplay that's enjoyable to read all on its own. I'd really like to see it happen. But given the accessibility of film and the logistics of filmmaking, making that screenplay would be really really hard.