Disagree that Julia solves the two-language problem, although it was a major step in that direction. It may currently solve it for specific roles (e.g. data scientists), but it does not solve it for general-purpose programming.

One specific example? Robotics and autonomous systems frequently use ahead-of-time (AOT) compiled binaries and libraries. You don't want your quadrotor / RC car / self-driving Tesla trying to perform JIT compilation while operating in time-sensitive scenarios. AOT compilation is a major Achilles heel for Julia--it's possible (with major limitations), but feels more like an afterthought than a core feature.

I can't see Julia scaling to general-purpose programming until its AOT compiling capabilities improve. JAX has some of the same drawbacks. I'm very interested to see if Mojo can fill the gap of AOT compilation with a reasonably simple syntax. (And yes, I am aware of Nim--I do wish its scientific ecosystem was more developed though).