Key phrase right there. Because it doesn’t matter what language a system is written in: if management doesn’t bother to hire replacements until after everyone who understands that system and why it works the way it does has already left, of course it’s going to crater shortly thereafter.

That’s not a language problem, that’s a business continuity problem. And it’s lamentably common as dirt.

Any monkey can learn to churn code. Learning the business domain, what its problems are, and how to solve them; that’s the bit that actually matters.

PEBKAC, at every level.