I think this depends on who you are. If you're the person who uses the same password everywhere, using SSO is a great idea: you don't spread the one password t

I think this depends on who you are. If you're the person who uses the same password everywhere, using SSO is a great idea: you don't spread the one password to that shady system that stores it in plain-text. You have control over the session token at your identity provider (assuming the RP service rechecks tokens as they should.) If you value privacy, and have a good password policy, you probably benefit nothing security-wise from SSO. You're still at the risk of MITMs or domain hijacking ruining the experience on that one site, which seems unavoidable. The question is where you store your passwords. You'd want it somewhere centrally for all your devices to share, and then you have a single master password. Depending on who you are, that might be OK. Passkey/WebAuthn has similar issues with how to share credentials.