IHMO junior develpers are not a problem. A customer of mine hired a developer at his first job after university. He graduated in Mathematics with some college level expertise of Java. We gave him an Ubuntu VM with Elixir and our Phoenix project and he learned to work and to use the language (the former is more difficult than the latter.) I think that learning Elixir was as difficult for him as it would have been learning any other language, including Java in a real world environment.

The problem could be with senior developers: if we had no experience with Elixir we probably would have resisted starting a new project (the main project of the company) with a new language. But this is the same with any language. Would I be confident to build a company on Python or Ruby or JS if I didn't know them well? Not at all. Would I start with Java? Not after all the years I have not used it.