Hard agree with you, Jordan. Yesterday I heard Seth Rogen speak with Lulu Garcia-Navarro on the NYT Interview Podcast (really worth a listen!) about how much the script changed in rehearsals for the film based on THESE specific actors and what THEY think about relationships and love. I really think this wonderful movie is a work unto itself that (beyond being so defined by its onscreen direction) is also just too linked with the actors involved. Seth Rogen's signature laugh is practically a leitmotif!
Non-theater people love to see one-location movies and say they "feel like plays." But I really thought this felt like a movie --- the voyeurism of the camera, the weird fourth-wall breaks, the switches in and (most importantly) OUT of theatricality --- I think it would have to be changed monumentally to work onstage. Which, maybe they'll do, and then it'll work like gangbusters, who am I to say? But it just feels like a weird IP grab to me.
"I feel safe with you, and complete with you / I'm always finding money in the street with you."
-Sheldon Harnick