There is an identical service available where custody is not relinquished: It's called coinjoin.
There is a difference between CoinJoin the protocol and the implementation of this protocol. We know the benefits of CoinJoin, we also know the danger of using the implementation of CoinJoin called Wasabi that is in cahoots with anti-privacy organizations.
It's like ECDSA. We know the algorithm itself is safe however there were implementations that were broken and leaked the private key when user signed their transaction.