[nybble41]

Don't let the user set the password, just assign them something random. If you let users pick their own passwords some of them are guaranteed to pick insecure ones (i.e. anything which isn't random and unique to that site).

Though frankly we should be able to do far better than one-off shared secrets for each account. WebAuthn, for example, with the browser as the authenticator, protected by either a client-side master password or biometrics. That would be at least as good as a password stored in a password manager, with the advantage that the user doesn't need to store (and sync) unique passwords for every site. To log in from a new device just enroll a second authenticator.