This is such a strange article. It starts out describing how Haskell was well-suited to their problem (or at least tries to) and then suddenly says:
The thing is: Biilmann no longer uses Haskell. It’s not entirely practical. Not enough people know how to use it, and this is unlikely to change. “Haskell is like a programming language from an alternate future that is never going to happen,” he says. “It solves all these problems it promises to solve. But it’s so different that there is no chance it will become common.”
1. Haskell may be a very good language to use for this particular problem set, probably better than the languages currently used for it.
2. People in general don't use Haskell and will likely resist attempts to change that.
So in theory Haskell is a good choice (because reasons) but in practise it isn't (because developers in general won't be a able to understand/maintain the resulting codebase) so he is using something else instead that avoids this problem (but he may think is a less than ideal choice in other ways).
I still have several services written in Haskell running in production and they've been rock solid for years now.
For the kind of problems I used to solve with Haskell (typically tasks involving a bunch of concurrency and IO) I use Go now. Not because it's a better language, but because Haskell is so drastically different that having anyone else maintain these services would require tons of training. Meanwhile Go is extremely practical and very easy to learn.
The thing is: Biilmann no longer uses Haskell. It’s not entirely practical. Not enough people know how to use it, and this is unlikely to change. “Haskell is like a programming language from an alternate future that is never going to happen,” he says. “It solves all these problems it promises to solve. But it’s so different that there is no chance it will become common.”