This is pretty sound advice for any language. You always want most of your code to be dumb. You save high abstraction for things that have a sensible interface and are common enough to need DRYing. Haskell has a higher abstraction ceiling than most languages and there is less trodden ground, so there may be more opportunity to get lost down the rabbit hole. However Haskell2010 is a beautifully simple language that can solve all your problems (maybe with a bit more code than enabling 20 extensions will afford you).
I had a similar experience with a different language at a startup where one programmer particularly would produce the most horrid code, use new features and libraries where they weren't needed, generally overcomplicate everything. He was smart as hell and made that smartness a liability for everyone else. The bottom line in a business is the bottom line; making money. He didn't understand that at all. No level of abstraction was too high, even trivial stuff. Dumb code that did the job well... dream on.
