So you're saying you want a federated wiki that uses a blockchain??? Genius.
Kidding aside, you're absolutely right. Wikipedia is one of the very few if not ONLY examples of centralized tech that ISN'T absolute toxic garbage. Is it perfect? No. From what I understand, humans are involved in it, so, no, it's not perfect.
If you want to federate some big ol toxic shit hole, Amazon, Netflix, any of Google's many spywares -- there's loads of way more shitty things we would benefit from ditching.
Edit: the "federated Netflix" -- I know it sounds weird, but I actually think it would be really cool. Think of it more like Nebula+YouTube: "anyone" (anyone federated with other instances) can "upload" videos, and subcription fees go mostly to the creator with a little going to The Federation. Idk the payment details, that would be hard, but no one said beating Netflix would be easy.
And federated Amazon -- that seems like fish in a barrel, or low hanging fruit, whichever you prefer. Complicated and probably a lot more overhead, but not conceptually challenging.