That's actually can be circumvented rather trivially. Wallets are anonymous, and you can just do some mixer transactions off chain. Wallet A pays to mixer M, mi

That's actually can be circumvented rather trivially. Wallets are anonymous, and you can just do some mixer transactions off chain. Wallet A pays to mixer M, mixer's address N sends funds to wallets B and C minus comission. In effect A paid B (and C), and nothing links them to each other. Schemes can get even less transparent with Lightning network.