One problem is that no format would solve the "who's in the room with you problem". You still need some kind of backend for that.
You could see a future though where you go into one portal and you're in Minecraft, and you go into another and you're playing tennis with your buddy in Europe. Games would just be new portals -- the key here is that it's hosted by different companies, not Meta.
Starting fresh could easily be the reason it's failing again because much time is wasted in reinventing the wheel.
The problem is still the use case not the tooling.