This is a good and well-written article, but it's worth noting that I think many of the ideas here cut slightly against the grain of current Haskell best practices. Which is not to say any specific part is right, but for example the entire discussion on QuickCheck is hard to really make sense of and arbitrary is a famously good use of type classes.

Probably the most countercultural paragraph is the paragraph on recommending you make a fresh type rather than reuse an existing type. I think that you lose so many useful operations eschewing maybe for your uniquely named Maybe [1] that a type alias is probably a much better call there, and also captures what you meant more generically. Further, stuff like Maybe over a more specific instance works much better with valuable tools like Compose.

Similarly, the redundant constraint on Empty is the sort of thing that will only trip you up in the real world.

All in all, great article tho.

[1]: People underestimate the compiler cost of deriving instances. It adds up very fast if you derive lots of functors and foldables in your quest for unique names everywhere.