I don't mean that the languages are not legitimate, mostly what would be acceptable to either management or a client. Also, I feel that setting someone up with code that they might have to maintain if I leave should be easy for them to handle and J, APL, or K would require them finding a rare developer.

Both are reasonable concerns. If you were running your own company the calculus might change though. Or not but I’d say it certainly could. Similarly for code which is not client facing.