OIDC doesn't scale, and OIDC Federation is still in draft. SAML Federation is mature with wide support and good discovery UX thanks to SeamlessAccess.
SAML has a variety of standard attribute bundles, entity categories, frameworks, and profiles covering important integrations, e.g., identity assurance. These are slowly being defined in (or ported to) OIDC.
I like OIDC and think highly of the people working on it, but it's nowhere near as cut and dry as you suggest.
I think... it probably is as cut and dry as I'm suggesting.
The things you just listed sounds like unnecessary complexity that inevitably leads to the “too big standard” problem, where every vendor and id provider has their own half assed, incomplete and incompatible implementation of the standard, or worse - with security bugs. Something quite often seen with SAML.
That’s not to say that oidc or oauth doesn’t have alignment issues. See https://news.ycombinator.com/item?id=35713518 “We implemented OAuth for the 50 most popular APIs. TL;DR: It is still a mess”