[JasonSage]

For certain there will be de facto community centers in open source games, but the fact that a group _can_ self-organize, self-fund, and self-moderate means that communities _will_.

Mastodon is I think a good example of this in social media.

A game example is Team Fortress 2, where community-run servers coexist with matchmaking servers. Some of these are buy-in communities, some of them are freemium ad-ridden servers, some are just small friend groups. And they can pose an alternative to official matchmaking on merit and exist just fine. Oh, and they can remove cheaters and bots themselves.

This is a good example to your last point: when the de-facto league has cheaters, bots, or lack of moderation, people will flock to alternatives en masse, but the alternative has to exist for it to work. This isn't a "problem" with the open-source game, it's the main feature. It's the bridged gap between "building your own game" and "the official huge playerbase game" -- they're almost the same out-of-the-box, so neither the building nor convincing is insurmountable, they're surface-level.