For a smaller company, that doesn't have the ability to dedicate a team of people to authn and authz, OIDC/OAuth/SAML/etc are all extremely complicated tools that take a lot of experience to even begin to understand the terminology. Ask your average engineer to implement logins for an API they'll be able to do it. Ask your average engineer to implement current SSO-like integrations for even the most standard of use cases (website logins) and it's a huge pain. Drift ever so slightly off the beaten path (IoT devices for example) and you're in for a "fun" time.
What makes OIDC a "non starter"?
I see OIDC as an implementation detail, and have no strong opinions about it.