I’m curious what led to that conclusion. As far as I remember, making concurrency easier to manage was always presented as one of Clojure’s primary objectives. It’s fundamental to the design e.g. a major motivation for all core data structures being immutable.

STM, atoms and agents were there from the beginning. I think futures and promises were added in 1.1. core.async is from 2013. Even popular third-party libraries like promesa and manifold are around 10 years old at this point.

I think flow promises to make it easier to orchestrate core.async, specifically, in complex applications, but the essential primitives are far from new and I don’t consider them any harder to use than JavaScript.