how are C/C++ disproportionally hard? the concept of multi-threading is the same for any language that supports it, most of the primitives are the same, and it's really not a lot nor complicated code to implement those.
the difficulty totally lies in the design... actually using parallelism where it matters. - tons of multi-threaded programs are just single-thread with a lot of 'scheduler' spliced into this one thread -_-