You completely missed the point of the article. It isn't about why Python & Haskell are good or bad languages, it's about how learning them doesn't necessarily improve ones' ability to work on projects with other developers, in unrelated languages.
There are social factors in language choice, it isn't just about the quality of the language itself.
And my point is that every language is flawed. If you only focus on the unique features of the languages you learn, you may not become a better program when working with languages that lack these features. But simply assimilating these ideas will do quite a bit to improve your productivity as well as your wisdom when designing systems because you will be alert for inadequacies that you would have missed before.
There are social factors in language choice, it isn't just about the quality of the language itself.