It's not as simple as you're suggesting. With Closure you sometimes have to rewrite otherwise correct and idiomatic JavaScript significantly to avoid it breaking during compilation.
The entire JS toolchain lost five to ten years by not adopting Closure. I suspect that in a year or two, someone will release a webpack plugin that does the exact same thing Closure did, with the exact same constraints.
In other words, CLJS users don't have to do anything special to benefit from the power of Google Closure. It just works :)