For me it is language instability. I was trying with Hy multiple times, but every new release they would break something, mostly by changing or removing core functionality (eg. removing let/cons).

To me, this looks like kids playground rather than serious project.

If Hy developers doesn't know how to evolve language properly, especially hosted one, which is challenging for itself, I'd suggest they look at Clojure or take some proper language development course.