Caveat before reading my comment: this article is from 2007 and the scene 8 years later is pretty different but the spirit still holds, I think. The author also specifically placed "pet programming language" in the article's title which makes my reaction to it a bit unsound since, for example, Haskell is not a "pet programming language".

WhatsApp built a 19B product on-top of Erlang. I'm building our startup's product on a mix of Haskell and Erlang; so far it's going well.

There's pessimism in this article that neglects to acknowledge adaptability. I agree to a degree with the thought that if I chose to build our product on-top of Idris I would be spending more time building tooling and dealing with immature parts of the language than I would actually building the product.

This is not the case with Haskell and other innovative but mature languages / platforms. Once at a certain size we may need to train programmers or develop some tooling internally but I see that happening even with Java and C++.

If you can boot up the product with the language / platform effectively and quickly, it's good enough to tackle a 100M product and adaptability can take care of the long-tail.