> Erlang sidesteps the problem by avoiding mutable shared state

Erlang is maximal shared mutable state!

Processes are mutable state and they’re shared between other processes.

Shared mutable state is hard to work with, but Java threads and Java promises both give you access to it. In either case, you'd need discipline to avoid patterns which reduce concurrency.

From the article, it seems that Loom (in preview) enables the threaded model for Java to scale. IMHO, this is great because you can write simple straightforward code in a threaded model. You can certainly write complex code in a threaded model too. Maybe there's an argument that promises can be simple and straightforward too, but my experience with them hasn't been very straightforward.