[brookst]

No complaints with questions, but many of the questions are in the form of assertions that are incorrect.

"Does that mean that passkeys can't be shared between users or devices?" is a 100% reasonable question.

"Passkeys are a step backward because they can't be shared between users or devices" is not really a question, it's an opinion based on imagination.

And passwords are just as complex. How do you securely share a login with another user?

Yes, there's complexity, but it's complexity born of a change in paradigm. The actual new thing is either equally simple or simpler than traditional passwords, once you factor in scenarios like backup, transfer, multi-device sync, sharing, etc. It's just different.