Most games that I know use a master server to connect players in multiplayer. If it ever gets shut down, without third-party software or master server, the game is effectively unplayable in multiplayer, sometimes not even in LAN. Temporary shutdowns can arguably be worse than permanent, because in the latter case you will likely have a community solution soon, in the former you have to wait for an unknown amount of time.
Assuming good intentions of the game developer, how can such a game be constructed so it remains playable? Can matchmaking be made fully decentralized? Do such solutions already exist?