The availability of developers is definitely something that should be considered when choosing technology. That said, NoRedInk, one of the companies earliest in adopting Elm have said they have had an easier time of hiring after they change to Elm from React. They are at least an indication of the opposite of what you are suggesting.
Also in Study of Programming Languages Not to Learn in 2019:
"As a final word, we wanted to reiterate that while the languages that didn’t perform well this year are useful and powerful in their respective fields, they may not have ranked as highly on our list because of the three metrics we chose. Therefore, if you really want to learn Erlang, Elm, or Lua, go for it — after all, these languages may make a comeback by 2020 because of your interest in them!"
I think one has to take the result in that article with a grain of salt as they only look at a very limiting set of metrics.
Also in the specific case of Elm I would recommend that people give it a try as it is a very different programming language than the most common languages and a great intro to the realm of strongly typed functional languages and functional thinking in general. Even if you don't end up liking or using it, it is a good thing to have experienced. There is always something to learn from learning new programming languages! ^^,
Personally, I would love to spend some time learning Elm. My point is not about Elm itself, but how smart it is to choose Elm for a project in 2019, at least in Norway.
Elm was chosen in 2017, and initial development was being done by 2-3 developers. Now, development is being done by 15-20 developers. Some of those developers came because of Elm (like me) and some came because our problem domain is interesting, and then learned Elm on the job.
Choosing Elm for a project in 2017 seems to have been a very good move.
Elm could completely disappear from the face of the Earth next year, and I'd still be glad I learned it, and would still recommend it to others. The concepts have made me a better programmer in general, whether in Node, React or vanilla JS. Hard to explain until you've actually used the language.
