The "level of productivity" when writing a browser app is going to depend completely on your other skills as a developer and not on the superficial differences between JS and Cljs. Only language zealots say Cljs gives them "whole new levels of productivity" over JS, learn to recognize them and ignore them.

For many, learning Clojure can make them better developers but most don't keep using it once they realized they can apply all the hindsights they learn from Clojure to a more productive ecosystem.