This is one part of the CLJS story that I think prevented it from becoming more widespread - it lacked a good REPL/compile story for a long time because of closure compiler. I would almost characterize that decision as a premature optimization - they focused on producing small output from the start, IMO larger JS size wouldn't matter that much in majority of use cases (you won't use CLJS to write websites, and webapps can tolerate few hundred k or even a MB of JS that's easy to cache), but they gave up one of the signature strong points for CLJ/Lisp so it wasn't as attractive even to CLJ devs.