It’s become harder to get clean(ish) audio captures for theater films, but it’s not impossible. There are still theaters with hearing impaired seating and headphone hookups, still a few drive-in theaters that broadcast via FM (one of those here in Reno, actually).
If anything, I think it’s because digital rips/DLs seem to come out more quickly. By the time a group has tracked down a clean audio stream and takes the time to sync it with footage, someone’s probably snagged a digital copy and released it.
Now Telecines, those are basically unseen these days. Almost no theaters still use actual film, and the few that do are way more careful about their inventory management. Gone are the days when a whole film can just get “misplaced” for a few days while someone with a Telecine setup copies it, to say nothing of how few people have the setup for Telecine anymore in the first place.
I keep Plex as a backup because some client devices are really tetchy about interacting with Jellyfin. Not every smart device supports the Jellyfin app (nor VLC), and if they do have a built-in media player it’s typically one that uses filesize-based progress tracking, i.e. you wind up being unable to fast-forward or rewind the video (or sometimes unable to even pause). Generally every major brand of smart device has a version of the Plex app, for better or worse.