As someone with a vested interest/being/been many of the parties you mention... Do you think support for "federated login via OIDC" would _not_ fall under the SSO tax?
Who do you think would host the "federated login" system that would replace the major authentication companies?
You can already stand up a SAML or OIDC provider using OSS and run the IdP for your company. I have many customers that do! And you bet we still charge them for SSO, and that they're every six months asking how bad the migration to a "big auth company" would be.
With dynamic client registration, I could host my own IdP server at home, or with a provider of my choice, and it would just work everywhere without any coordination work for anyone, manual signups to be assigned a client id/secret, etc. The entire point is that you won't let me do that because you want to charge extra for better, simpler, cheaper security for everyone. That is the SSO tax.
I should be able to just give my email or domain name, and it kicks off an oauth flow to that domain no matter who I use for my email/identity. In the same way that I can give you my email address and you'll just email me without me having to pay extra for enterprise email.
Who do you think would host the "federated login" system that would replace the major authentication companies?
You can already stand up a SAML or OIDC provider using OSS and run the IdP for your company. I have many customers that do! And you bet we still charge them for SSO, and that they're every six months asking how bad the migration to a "big auth company" would be.