The problem with this is requiring everyone to own a device with a secure enclave or similar hardware capabilities because some people are prone to being phished. Let me choose the level of risk I find acceptable.
Passkeys don't require it, but relying-parties may: https://github.com/keepassxreboot/keepassxc/issues/10407#iss... If enough RPs ban clients that let users manage their own data in the name of "security," then it is effectively required by passkeys. The passkey spec could have been written to be resilient against this type of abuse, but instead this abuse is explicitly considered a feature of the spec.
Are there any credential managers that don't validate the domain with passwords? Sure, there are issues with PSL subdomain matching, but at the end of the day it's good enough in the real world. All the other stuff (MITM, malicious site, etc) falls under the other case I already mentioned.
It's security, so we're not discussing impossibility. You can still phish a passkey, we're just hoping the cryptography is good enough that it remains astronomically unlikely to succeed. Since we're all reasonable people, that chance is low enough that we're fine accepting it. What I'm saying is that the chance with passwords is still low enough that I'm fine accepting, even though it's much higher than the cryptographic security of passkeys. We're simply disagreeing about where we draw the line of "good enough".
You crack the private key and forge the challenge? Maybe the other IDs sent alongside it are hard to get for some reason, but the security of passkeys comes down to the cryptography. Cryptography can always be broken, but a good cryptosystem makes the probability low enough that any reasonable person considers it good enough.
If you trust that the cryptography employed in passkeys is effectively unbreakable, then it follows that for all intents and purposes, passkeys cannot be phished. It’s the same thing as trusting that your browsing sessions cannot be MITMed because the end to end encryption is sufficiently strong.
