The motivation of Clojure, to me, is making concurrency safe and easy. So far, the best way to reduce "risk" in concurrent systems is to constrain side effects,

The motivation of Clojure, to me, is making concurrency safe and easy. So far, the best way to reduce "risk" in concurrent systems is to constrain side effects, and not share mutable state between units of concurrency. If you're choosing to reduce the number of side effects, then a functional language is clearly the best suited for the job. The creators of Erlang knew this. The creators of Haskell discovered(?) this. In my opinion, the fact that Clojure is a lisp is completely irrelevant, personally I prefer ML-family syntax, but the consistent standard library of Clojure makes it too powerful to ignore. The focus on concurrent programming is also indicated by its relaxed stance of side effects. It is not a pure language, it only sets the constraint that you cant have side effects that leak state into other units of concurrency. If your mutations don't create a risk of data loss, then you are welcome to use them.