AAD implements SAML, OIDC, SCIM, LDAP, Kerberos, FIDO2 and more. Even if it was not a Microsoft product, it would have better non-proprietary interoperability than most other SSO platforms.
How so? I'd argue they're far ahead of the competition in features.
Except for all the basics like RBAC with multiple roles, JWT modification, simple MFA, etc.