There is no doubt a steep learning curve with Haskell and FP in general. You may be thinking: what is all this <$> <*> and $ nonsense! However once learned, you can look at the Haskell code and it is more clear precisely what it is doing (and what it can't possibly do).
I think the article undersells Haskell. Haskell gives you code purity. Purity means you can reason about a function. A function that takes in an Int and returns an Int won't read data from your disk. It won't call a web service to get the answer. It won't update the counter int on your class and then one day cause it to overflow, causing another class that reads the counter int to throw an exception. This makes maintaining code a hell of a lot easier and more pleasant.
There is no doubt a steep learning curve with Haskell and FP in general. You may be thinking: what is all this <$> <*> and $ nonsense! However once learned, you can look at the Haskell code and it is more clear precisely what it is doing (and what it can't possibly do).
I think the article undersells Haskell. Haskell gives you code purity. Purity means you can reason about a function. A function that takes in an Int and returns an Int won't read data from your disk. It won't call a web service to get the answer. It won't update the counter int on your class and then one day cause it to overflow, causing another class that reads the counter int to throw an exception. This makes maintaining code a hell of a lot easier and more pleasant.