The idea isn't that a human gets one uuid to be used everywhere, but that each site gets one of the human's many uuids. Someone still needs to track which uuids belong to which human, but at least it's not a random, possibly insecure or disreputable website.
Technically, yes. Crypto is anon. Right up until there's a leak or a slip up that links your wallet address to your identity. Then just go through the entire history of the ledger to see every transaction that's ever happened with your wallet.
