> On the other side, Elixir and Erlang are not that popular and every time I talk about it to other developers, they may have heard of it but can't talk about it, so it's probably not that easy to find devs for a startup.

This was the exact issue we encountered after I had switched a startup's backend from Node to Elixir. I was able to churn out features pretty quickly (and the switch itself turned the core batch job underlying the product from a multi-hour runtime to less than a minute), but the bus factor was pretty much 1 and we were never able to really increase that before the company ended up running out of runway and folding.

This was almost a decade ago, though, so things have hopefully improved somewhat.