Watch Together is also being removed
Which got a lot of people (including me, also a lifetime subscriber) in this thread absolutely livid: https://forums.plex.tv/t/allow-watch-together-for-tv-shows-m...
(We were begging for them to fix the functionality of watch together for almost 5 years)
Plugins, the watch later list, the up next/playback queue, Plex Cloud/Cloud Sync, photo backup (this one hurt), privacy preferences were badly nerfed.
Those are just the ones I miss, I'm sure there are more (like the short lived arcade thing).