Passkey is some sort of specific unique key to a device allowing to use a pin on a device instead of the password. But which won't work on another device.
Now I don't know if that key can be stolen or not, or if it's really more secure or not, as people have really unsecure pins.
An online authentication system is quite literally the one central thing your whole digital life depends up on. If it's broken, it can completely f'up your life and remove you from existence in the digital space. So there is extremely good reason to be skeptical when big-company tries to force you into a new thing. Especially when said big-companies have a history of f'n things up on purpose (remember G+ forcing real names on everybody and bundling previously unrelated accounts into one monolithic one?). Or take HTTPS, which was sold us with "bringing more security", when what it actually did was kill large chunks of the open and self-hosted Web.
Are you seriously arguing against HTTPS?
Yes. It's one of the major reasons why the Web turned into a cooperate controlled hellscape. Note, I am not arguing against encryption, just against HTTPS crappy implementation of it. It's also going to get even worse with QUIC.
HTTPS is definitely not a major reason the web turned corporate. It has its problems for sure though.
Look at Gemini if you want an example of a decent web ecosystem that has HTTPS as a requirement for the protocol.
Gemini benefits from two things that the web has lost: