This looks appealing as a framework for using in IAM for applications with federated auth. Given historic legacy alterantives are lower level policy frameworks

This looks appealing as a framework for using in IAM for applications with federated auth. Given historic legacy alterantives are lower level policy frameworks like RADIUS/TACACS, SAML, XACML and UMA2, what are the objections to Casbin? A library you can build into your application for doing policy AuthZ without having to deal with a centralized policy repository, while moving AuthN to your IAM gateway is a huge deal in enterprise envirionments.