> For various reasons, Terraform was ditched in favour of a python-based boto3 solution, and one of those reasons was that the restrictions of a more declarative language produced more friction than the benefits gained.

I feel the same about CMake. It's horrendous and everything would be much simpler if you could use the full power of an imperative programming language. Conan on the other hand is Python-based and essentially a framework (though for a different purpose). With a nice set of built-in functions and a clean interface design, I believe that using a full programming language gives you many of the advantages of declarative languages without the oddities and an easy way to drop down to a lower level.