Go early in the morning. The 10:00 am Sunday showing of Oppenheimer is likely full of movie buffs.
Go midweek. An emptier theater reduces the impact of phone screens if someone uses one.
Go to nicer theaters with higher numbers of staff.
Go to niche theaters. The non-profit place with the weird snacks is likely filled with movie buffs.
Go to classic movies you missed the first time around.
Actually, it looks like the one in Sherman Oaks has survived relatively tact under new management (now known as The Culver Theater) but I haven't been so cant comment on the experience.
> Go to classic movies you missed the first time around.
YMMV.
I did this in a nice little theater with a single room. They didn't even sell any kind of snack, just drinks, if that. Went to see an older movie, but a fairly long one (children of paradise). It was a nicer day, too, so not one where people didn't have much else to do.
Cue a bunch of insufferable twats eating a truckload of chips during the whole show, complete with the noisy bags and everything.