Passkeys are never going to be possible without fallbacks, for the same reason that hardware keys aren't possible: people frequently lose their devices.
And if people let Google handle their passkeys, then it's equivalent to going all in the Google Social login.
Passkeys have absolutely no advantage over using a password manager. If your browser can generate, store and autofill passwords, then we're talking about the same level of convenience.
I don't mind passkeys, but that's only because I use them with a cross-platform password manager that I can trust. And it will be a really long time before I recommend the use of passkeys to my family and friends.
