I work in the space, and your experience is accurate to mine as well. I think it's important to keep in mind that the hard part of OAuth/OIDC has nothing to do

I work in the space, and your experience is accurate to mine as well. I think it's important to keep in mind that the hard part of OAuth/OIDC has nothing to do with the core federated authentication flow. The complexity comes from several other known hard problems: federated trust, AKA how do you on-board federated trust between business entities using short-lived, easily rotated certificates? And federated authorization, AKA how do you codify the taxonomies of user roles and application permissions as an API contract between diverse businesses and apps? Both are known hard problems.