OPA, or rego? My experience working for Styra was that most people seemed to grok where OPA fit in fairly quickly, but struggled with rego. It's a very powerful language and well worth learning I think, but it's an investment for sure.
Rego is a DSL and the main purpose of DSLs is to simplify things (compared to general purpose programming languages), so in my opinion Rego is not a good DSL.