Trust me; I am stupid, but last time I checked it took a literal crap-ton worth of code for a Unity-made game to be multiplayer, because Unity doesn't support cross-device multiplayer (Like COD or other multiplayer games/MMOs), meaning Fish'd need to either port the game to a different client so it can have multiplayer, add the code that allows for cross-device multiplayer, or just leave it be for the time being.
It's Fish's choice as to what he wants to do with the game, we can only influence him so far