I don't understand the fixation on hiring $LANGUAGE devs. If you can't find any developers using your current stack, pay for a course or a book for them and train them on it. Training a competent developer to use a new programming language has to be easier, cheaper, and faster than rewriting your entire software stack.

You can always find stories of people moving off of stacks. Sometimes they just legitimately evolved in a direction the stack wasn't the best solution for. Sometimes they should never have picked the stack in the first place. Sometimes a new leader came in who had preconceived notions that the company needed to conform with. You really have to look at the specifics of the story to know if it's relevant to you.

In my very opinionated opinion, it's actually reasonably uncommon for me to read a story of someone leaving a stack and not classifying it as one of the things I listed above. Of the cases I would consider "legitimate", it's usually a performance issue; some languages and runtimes are just intrinsically slower than others, or at least, intrinsically slower without an unrealistic amount of effort. (Elixir would be middling here. BEAM is kind of between the dynamic scripting languages and the compiled languages. The interpreter is simple enough that it can run much faster than the dynamic scripting languages but it would be completely unacceptable performance for any compiled language. You can run out of performance in BEAM, but it does take a system that needs performance and some growth to get there.) The rest are probably complexity explosion of some framework, and this is almost always a UI framework problem.

Divvy still uses Elixir extensively. I use to work there and still have many contacts there.