Except they have no story for building composable libraries in a distributed setting. The story for distributed execution in Julia today is just use MPI, which is a terrible answer. Anyone who has ever use libraries backed by MPI in any language knows that they are inherently not composable. You can't just take an object partitioned across multiple nodes one way by one library and pass it into a second library that expects it to be partitioned a different way. As far as I can tell the Julia language has nothing to say about that, and that makes them a non-starter today for anyone trying to build composable libraries for distributed memory machines.