Comment by BiteCode_dev

I quite like CUELang (https://cuelang.org/), although it not yet widely supported.

It has a good balance between expressivity and readability, it got enough logic to be useful, but not so much it begs for abuses, it can import/export to yaml and json and features an elegant type system which lets you define both the schema and the data itself.

I hope it gains traction.