Quality is fine, sounds like user error. Features sure, but that’s to be expected with a paid app.
Show me an AppleTV JellyFin client that “just works”. Something my mom & dad could use to watch a movie. Something that can do normal media player things like seeking or subtitles.
There is a huge disparity in the quality, support, and features of the various clients.
I set my parents up with infuse and it works fine with no issues. To be fair apple doesn’t seem to be very supportive of foss development on their devices
I don’t use Apple products so I can’t speak to the AppleTV support.
But your criticisms seem to be of clients for Jellyfin rather than Jellyfin itself.