This isn’t such a bad idea, although maybe it should depend on the type of game. As a kid the only place I played games with random people was Quake servers and Battle.net. This wasn’t really an issue, as there’s not much time to socialize when you’re blowing up your opponent. But Roblox seems to be primarily a social meta-game with many sub-games, so it’s riskier.
It’s a spectrum. On one end you have Second Life and VRChat, which should absolutely have a no kids policy. At the other end you have single player games which are obviously fine. In the middle there’s everything from online Mario Kart games to Counter Strike. Some are probably more ok than others. As it stands Roblox is uncomfortably close to the no-no zone.