Learning about those things is different from actually using those in production. J/K are indeed very, very interesting languages.

Not sure about you, but the software we are forced to use at work is never as pleasing as the software we can use at home.

I managed to use J at work. Kicked the crap out of a 240 core spark process on one thread. It really is an amazing technology, and people ignore it and lessons of the past at their peril.