The only time I've seen "the game where you can do anything" work out is VR Chat. But that's only because "anything" here means "anything you can make in Unity

The only time I've seen "the game where you can do anything" work out is VR Chat. But that's only because "anything" here means "anything you can make in Unity and publish to the servers", so it's less a game and more a multiplayer creative experience.