The current main issues are:
- Custom games are broken
- Co-op experiences regular disconnects
- Halo 2 classic audio is broken
- Cheaters can impersonate other players and get them banned
- Matches sometimes fail to load leaving you stuck on the scoreboard
- Ranked playlists have long wait times due to matchmaking criteria being too tight
Mint Blitz has a 92 point wishlist for fixing the remaining bugs and another serious issues in a final update.
Coop Issues fixed, 4 player coop for select games, is 4 player CE campaign possible? Splitscreen disconnects and various other splitscreen issues New Rotational Playlists, community driven content to sustain the game for years to come. Steam Remote Play Together Modded Custom Games Browser, Mods ...
docs.google.com
It doesn't need years of active development; just basic features like co-op working as they should.