You have to start with the 'simplified but not technically perfectly correct' and then add in the nuances to get to the real point. Starting with words like 'functors' that most software engineers today will not be able to define is not useful.
But the parent post https://news.ycombinator.com/item?id=28476325 to which lmm was responding https://news.ycombinator.com/item?id=28476569 said "Wait, a functor is just a pure unary function?" If someone asks you the definition of a technical term, you sort of have to at least refer to the technical term.
Learn You a Haskell mentions functors in chapter 8 and teaches them properly in chapter 11.
http://learnyouahaskell.com/making-our-own-types-and-typecla...
Regardless of how LYAH chooses to order things, (when have you used a Zipper last time?), they are too essential to any beginner Haskell program.
In my opinion we need a new imperative first approach to Haskell teaching, to develop intuition on monads quickly.