Also one big deal is how Apple handles key distribution. They absolutely could MitM that connection to get access to the user's keychain and the UI doesn't real

Also one big deal is how Apple handles key distribution. They absolutely could MitM that connection to get access to the user's keychain and the UI doesn't really give the user any feasible way to detect that Apple has added their own key instead of just the key for your other device that Apple doesn't control. It's "end to end encrypted" but if you just handwave away key distribution and leave that up to Apple, what's the point other than a marketing gimmick?