This rumor persists for so long. I’ve been in tech for now twenty years, and juniors say this all the time. Also, I’m hired to replace archaic code with modern equivalents, so my perspective is one from the other side.

A few key things I discovered:

1. Companies that need devs of an archaic language are extremely rare. I’m talking about like you won’t see it on job boards until they already have 1-2 people in mind already.
2. Usually the people they hire have been doing only that for years. Usually retired computer scientists or professors.
3. The pay isn’t high at all. I remember seeing a position that needed THIRTY years, and their offer was nice, but low on the tech side. I made double the salary. If you work at META or Alphabet, you’ll be making 4-6 times as much.

Finally, those archaic systems get forced into retirement. Yes, there are still integrated systems like ATM and missiles or whatever that use these languages.

But that’s so extremely rare that they’re still being maintained. Because companies will allocate a budget to have some dipshit programmer like me come in, rewrite the functionality in whatever language (the last one I did was a interface from a PoS system to a web application, which I did in PHP), and then throw away the code.