I'm sad I missed OpenID. Would've been fun to be able to set up my own identity provider for a while until websites would eventually stop supporting it.
I didn't miss the OpenID days. Basically everyone was a OpenID provider (i.e. all of them offered to handle your accounts for you), but no one was an OpenID consumer. Even at its heyday, I don't remember any single service where I could login with my OpenID except for the websites I made.
StackOverflow was one such service (or still is? not sure...).