Passkeys is an interface between your password manager and a website without all the fluff with filling or copy-pasting passwords.
I don't love them. I don't love passwords either.
But while I don't fear passwords, I fear passkeys. The reason is that it makes the tech even more intransparent. My password manager stops working, completely dies or I can't use it anymore for other reason? No problem, I can fallback to a paper list of passwords if I really have to. This transparency and compatibility is more important than people think.
Passkeys lack that. They can be an interface like you described, but only if everyone plays along and they can be exported. But since there is no guarantee (and in practice, they often cannot be exported either) they are not a replacement for passwords. They are a good addition though.
Unfortunately, many people don't understand that and push for passwords to begone.
And I would agree with that argument.
It's literally something like
hnkTKS7h2WCOBr3CxSKM51cSVKSkiKOSlQsMhtRZ0CU
stored in the password manager.