I mean, the fact that more than half-century-old COBOL continues to be maintained does speak to the fact that it is maintainable. That might also be part of what makes COBOL painful to the average developer: You’re not only dealing with a language that first appeared in 1959, designed for machines that were very different than modern computers; you’re also dealing with over a half century of legacy code, including all that means for Hyrum’s law.

Unfortunately maintainable and pleasant to work with are rather distinct concepts.