I've recruited and built a team which was writing code in Elixir, even more obscure than Erlang. It wasn't really a problem finding people who knew it or were strong programmers who were interested in it.
Good languages attract good programmers.
The idea that we need to stick to popular languages is, I think, driven by business guys who want commodity programmers.
If you want 100 engineers added to your team in a year, then sure, use Java. But you will still be less effective, I bet, than 10 engineers doing erlang in that same year.
I would argue that you can pick any new'ish (last 5 years) language that is suitable for development and find the same results. Anyone who knows the language well taught themselves how to use it without the guarantee of being able to use it at a job.
This will be a fairly small subset of developers, the ones that have motivation and time to put into growing themselves. So this probably means that the devs that know new language X are just more interested in software development (compared to devs that just know the language(s) they learned in school, and whatever they were taught on their jobs). So they have a much higher chance of being good developers.
Good languages attract good programmers.
The idea that we need to stick to popular languages is, I think, driven by business guys who want commodity programmers.
If you want 100 engineers added to your team in a year, then sure, use Java. But you will still be less effective, I bet, than 10 engineers doing erlang in that same year.