Well, unfortunately, there is no project like that with Wikipedia’s critical mass. Most attempts with any attention are rather horrific. See: Grokipedia.
If Wikipedia dies, nothing good will replace it.
I know that’s a bit defeatist, but I really think its “the best we got.” Nothing better is coming with the state the internet is in now.
And I just want to emphasize that maybe a small community could build something better. I know.
But in terms of “keeping a healthy knowledge base for civilization,” that kind of project doesn’t matter if no-one sees it. Wikipedia is valuable because its a reasonably sane default reference for billions of people, that isn’t some megacorp or government.