You mean the website that's run by a non-profit, uses an open content license, provides full history dumps, and is maintained by hundreds of thousands of volunt

You mean the website that's run by a non-profit, uses an open content license, provides full history dumps, and is maintained by hundreds of thousands of volunteers? Wikipedia is hosted centrally, because running infrastructure in a decentralized way is worse in every technical sense. The actual content and maintenance is as decentralized as you can possibly have. I'm sure you haven't really put much effort into actually looking into this, but you can volunteer to work on the underlying software, and infrastructure as well. The wiki and infra code are open, the infra is documented openly, and the test/dev/staging environments allow volunteers to directly participate. You can have your code end up in production after review.