What very specific use case? I have found Cue to be versatile and usable anywhere yaml / json / config is used or needs to be validated. I'm mainly focused on code generation with Cue as the input. https://github.com/hofstadter-io/hof
I'd consider a situation where you've got a human readable (?) data format that needs to be validated a rather specific niche for a domain specific language. All I'm aware of in that area is XSD and DTD for XML (and maybe some recent efforts to make schemas for JSON but those aren't too flexible).
I'm happy someone is trying to fill that niche though, I'll remember cue for when I run into such a scenario.