ClojureScript is probably the largest community of consumers of Closure Compiler & Library outside of Google itself. However, I don't believe it's well understood why we continue to rely so heavily on the old style Closure namespaces and avoid ES6 modules.
The short version is that the old style Closure namespace delivers pervasive late binding which is essential for an interactive development style that simply isn't possible with any other popular hot-reloading tool - this includes React (Native), Flutter and SwiftUI.
Hopefully this provides some insight and some things to weigh when considering future changes to Closure and Closure Library.
Lead ClojureScript Developer