It's not really a configuration language like Jsonnet and CUE. It's an expression language for specifying things like conditions and policies. You _could_ abuse it as a configuration language, but it'd be overkill.
Yup, it's really a good fit for simple constraints eg in IAM systems. Give user X permission to do Y, but subject to some CEL expression like date comparison (auto-expiring grants), resource path prefix or similar.