selfhosted games used to be a thing on playstation consoles, starcraft, aoe, ...
Just abstract it enough and the common player won't notice or care, especially with a lot of people running off ftth connectivity with several-hundred Mbit uplinks and ultralow latencies.
Running off ipv6 natively gives you a direct connection to well-configured enddevices.
The main gaming problem with user-hosted lobbies is cheating as the sever runs sanitychecks. A gaming company could just run proxy servers for user-hosted gameservers