This article does not age well. Especially the C# stuff...
Also, using Haskell 'very little' will not give you the experience you need to write something like this. Haskell has a (very) steep learning curve and you need to recognize ways to solve problems and to see the elegance (and the warts as well by the way). That takes time and effort; maybe there are people who just get it, I am definitely not one of those people, but the work, for me, was definitely worth it.
The article agrees that it made the author a better programmer. The argument they're making is that it made them a worse C# developer. Their Haskell experience allowed them to see the specific problems with their C# code but didn't give them the tools to fix them because functional programming isn't (or wasn't) idiomatic C#.
why hasn't it aged well? re: c#, afaik LINQ would solve this particular problem, so perhaps the solution wouldn't be as verbose nowadays. but other than that it still rings true – I miss Haskell when doing Python and keep coming up with weird hacks to shoehorn functional stuff into it (ask me about the time i used async/await to implement something like do-notation...) which probably makes me a "worse" python programmer, same as TFA
Also, using Haskell 'very little' will not give you the experience you need to write something like this. Haskell has a (very) steep learning curve and you need to recognize ways to solve problems and to see the elegance (and the warts as well by the way). That takes time and effort; maybe there are people who just get it, I am definitely not one of those people, but the work, for me, was definitely worth it.