If the passkey protocol didn't support attestation, then that would be true. But since it does, passkeys aren't as good, since I can't make my own backups of them.
You can make your own backups of passkeys from your password manager.
I believe you are confusing ones that are stored in software or syncable (Passkeys) with the hardware backed credentials (platform authenticators).
The problem is that the protocol allows websites to require use of the latter. If the two were indistinguishable to the website, then passkeys would be a good thing.
The amount of people in this thread who don't understand the very basics of this stuff is a pretty good counterexample to the common trope they somehow "know better." I kind of doubt that when many people here can't even get the basics straight.
https://fidoalliance.org/specifications-credential-exchange-...