Today we use lots of accounts with unique passwords. Obviously these passwords have to be stored somewhere. So I disagree with you when you say it's a unique passkey thing.
Passkey has an advantage when it comes to phishing because it doesn't totally rely on human intelligence or state of mind.
From a personal experience my data was leaked online, not because of phishing or I was careless. but it was leaked from a well known third party site which I used. They were affected by a very serious breach. Many unlike me use the same passwords for their emails and stuffs. But in case of passkeys there isn't a shared secret. A breach will be useless.