Earlier quoted context omitted.
I struggled a lot too. I think the main issue is the problem domain in which these languages excel at. I like compilers, systems programming, distributed systems... but math? statistics? I'm admittedly terrible at that and find it really uninteresting. It doesn't help that most literature on J tries to teach its language concepts showing you how to solve math problems. I have no need for a fancy calculator. For what…
My general belief is that these languages would be far more useful as embedded languages; occasionally there is a need for the core of some complicated system to take advantage of their power, but the same design that makes them good at math makes them horrible for writing APIs or database access.
q especially looks mostly like a normal procedural language, and can be used like one too.