2FA exists because defense in depth. Even if passwords weren't phishable, it can still be handy to defense in depth that a person is who they say they are by checking multiple factors ("something you know", "something you are", "something you have").

Passkeys largely meet 2FA requirements by themselves because they are "something you have" (its stored on a device you own) and require "something you know" (device PIN) or "something you are" (biometric unlock) to use.