Making Infuse the Plex client Plex Media Player for Apple TV should have been is a great propsal. I can‘t agree more.
Infuse‘s metadata handling is rather incomplete, on the other hand it‘s playback capabilities are far better than the ones of Plex Media Player for Apple TV.
To be honest, I don‘t like those automated metadata fetching functions whether it is Plex or Infuse. Those functions only work 90% of the time and produce more problems and work in the long run for large movie collections than what they should avoid.
My regular process when transferring a newly bought bluray to my server is to also encode two m4v-versions of the mkv-rip at different resolutions and quality levels and embed metadata and bluray cover with Subler for macOS. If you set the metadata correctly you can easily handle multiple versions of the same movie (tag contentID), control display order for collections (tag SortName), etc. Storing three versions of a movie guarantees they all run well on all sort of devices: from high quality on the large screen to watchable on your phone.
The two m4v-files are fully iTunes- and Plex-compatible. iTunes for example can read a directory structure with 1000+ movies in just a minute or so. macOS and Windows will also display the movie cover in Finder or Explorer which is nice and when you move a file, all metadata will move as well.
Unfortunately I didn‘t find a way yet to embed the same metadata in the mkv-file. There is no tool for macOS afaik. Fortunately when using Plex, Plex simply takes the embedded metadata from the m4v-files and uses them for the mkv-file as well, as long as all three files are in the same single directory.
So, after setting up all movie and tv-show files on the server with proper metadata, Infuse would be the best Apple TV client to display and playback a movie collection, if it could connect to a Plex server.