Well, as it was said, it's using a (several) full-fledged programming language(s). If you are a firm believer in the "declarative" ideology you might see this as a drawback. On the other hand I can see from Terraform issues on Github that people sooner or later want something more turing-complete including loops etc. Then you might as well use a real programming language instead of jumping through hoops and trying to emulate stuff like that in your declarative language.