Passkey’s approach is actually relatively close to client side certificates. It’s just in a form that is compatible with using a password manager. From the user standpoint once everything supports it properly, logins become relatively transparent and man-in-the-middle is pretty effectively mitigated. The other upside is of course unless you’re hosting your own stuff, no one supports client side certificates. This is an opportunity for all the big players to actually push people into better security.