I wasn't around when it was adopted, but it definitely felt like someone joined the company, evangelized Elixir, hired maybe half a dozen people who were really good at it, and then left.
Eventually, our Elixir experts evaporated, leaving maybe two people who truly understand it and can do difficult work in it. That's not sustainable.
Someone else in the comments here said that a good developer can be productive in any language, and that's true - but why hobble people? It's like saying a good surgeon can be productive with a butterknife and a pot of boiling water, or a good artist can be productive with a charred stick.