Nelson demonstrating Xanadu Space
However he seems to have written a useful explanation of the less well understood parts.
Clearly there are ideas in Xanadu which couldn't be built that held back the bits that could.
Much exists because we weren't hung up on monetisation and MicroPayments the way Nelson was.
It's hard to see how Xanadu could have been built in one go rather than evolved out of earlier web experiments.
Obviously the immutability mentioned in the article might come about as there are many new BlockChain based immutable distributed file systems. Hooking a wiki up to one of them, via, say BeakerBrowser and HypercoreProtocol / would make this part plausible.
See also :