OIDC actually does have a discovery mechanism standardized to convert an email address into an authoritative issuer. Then, it has a dynamic registration mechanism standardized so that an application could register to new issuers automatically. Those standards could absolutely be improved, but they already exist.
The problem is that no one that mattered implemented them.
If you want to get anywhere with something like this, you need buy-in from the big email providers(Google, Microsoft, Yahoo, and Apple) and the big enterprise single sign on providers(Ping, OneIdentity, and Okta). All of those companies already do OIDC fairly well. If they wanted this feature to exist, it already would.
Instead, it seems like big tech is all-in on passkeys instead of fixing single sign on.