I wasn't really meaning to criticize the blog post. It's very intelligent and interesting. I just think the title is kind of silly and highlights how extremely complicated and impractical advanced functional programing theory and concepts can be if this is meant to present them in a "simple" way.
Perhaps I'm slightly misinterpreting the usage of "simple" here and it's related to the more technical notion of simply typed lambda calculus.
The techniques present in the paper and blog post are not really from functional programming but from mathematics. Functional programming just happens to present them in the most natural way; this is why the paper chose Haskell. We could implement the same in any Turing-complete imperative language, but then the code would swell by orders of magnitude.
I think you are still making an unfair generalization from this post. What you are saying is like reading a machine learning paper which has python examples and complaining that software development with python demands understanding advanced linear algebra.
Perhaps I'm slightly misinterpreting the usage of "simple" here and it's related to the more technical notion of simply typed lambda calculus.