Yeah, for sure there are some edge cases, and COBOL is a big one, since there's a LOT of banking/finance stuff built on it.

FWIW, my employer just deprecated our legacy COBOL (1-2 modules out of many), replaced with Java. It took years to make that transition.

I took a COBOL course during undergrad in 1998. Glad I was exposed to it, but I never did anything with it.