I recently gave a talk on this and agree. While it was fun to learn, the difference between oauth and oidc isn't clear. Especially with what I've been referring to as oidc "wave 2" - machine to machine authentication without OAuth seemingly involved at all.
And to be honest, this is part of the problem. We use confusing (and sometimes conflicting) terminology to describe both authentication (identifying somebody) and authorization (making sure you have the right permissions to do something).
More information: https://stackoverflow.com/a/1087071/19020