OAuth only does AuthZ. I've always found OAuth more complicated because you have to combine it with other technologies to get AuthN
AuthN: Authentication (who you are) AuthZ: Authorization (what you are allowed to do)
I've never had to clarify what someone is actually trying to accomplish when they want "SAML 2.0"
Since OIDC is better than SAML, which is probably the scariest security standard on the Internet, I think it's worth being clear to people that OIDC/OAuth is viable.
The SAML authz story, for what it's worth, is pretty shady.