The only thing I find is that StackExchange is dropping support because it’s not useful for them. It doesn’t say anything about the usefulness of the protocol itself.
I did before I posted my previous reply and I found https://www.gluu.org/blog/oauth-vs-openid-whats-the-difference/ where it says:
The great thing about OpenID Connect is that it standardizes the flow for person authentication using OAuth2.
So OpenID Connect is not an alternative to OAuth2, it’s actually a standard on top of OAuth2.
Not quite true, as with OpenID I can force a user to re-authenticate before they are sent back to my server by sending login=prompt with my request (see https://openid.net/specs/openid-connect-core-1_0.html#rfc.section.3.1.2.1), so I can be sure the user actually had to enter their credentials at the OpenID provider’s website, making it less likely that it a malicious user that is re-using an already existing session with the OpenID provider.