If you can run your own server then that's still a central server. That still lets a community of people work with a central authority. It's just a different authority from the game's publisher.
Most people can't run their own server, because they aren't on a public IP!
In that sense, Mastodon is a centralized service because it's on someone's computer. That's not really what people mean by central. They mean we're increasingly reliant on game companies for networking infrastructure.
Is that all IPV4s fault? I don't think so. But it complicates things