As for Kodi, it's somewhat of a different class of software to Plex/Emby/Jellyfin - Kodi is more a player interface for local files and with the option to install plugins to play from other sources like DLNA, or even from Jellyfin [1] (and I assume Plex and Emby as well)
Jellyfin is more a network player - your jellyfin server does the heavy lifting, like transcoding etc. so your client basically just needs a web browser (though there are native apps too).
The devs of Emby were always fairly hostile to the spirit of open source and when they closed the source in v6, the community's opinion shifted in favor of Jellyfin. As far as I can tell, Emby is pretty irrelevant now.
