You can even compare it to OpenID, where it languished mostly-unused—but still actively-maintained!—for 5-10 years before OpenID Connect (a hybrid of the ideas of OpenID and OAuth) became the basis for all the major Single Sign-On services in use today. I doubt OpenID Connect would have inherited any OpenID-like functionality (e.g. profile discovery) if OpenID had been deprecated a year after its drafting. They probably would have instead (badly) reinvented it with no knowledge of the prior art, because there wasn’t an existing (if small) install-base to prove out the practicality of the various features.