On the one hand I know what you mean: I know practically no category theory (basically I know enough to expect "co" as a prefix to mean "everything the other way around"), but I can still produce good Haskell code.

But on the other hand, I look at some of the stuff Edward Kmett has produced, particularly his lens library which I use all the time, and its very obvious that the design has been informed by a deep knowledge of category theory.