You do not need to be good at haskell to consider this idiomatic.
In my mind this is more about understanding how folds work and not writing their definitions for each individual case.
Similar thing is using map instead of defining your function to iterate over lists in a way that map does it. (I mean writing f = map g instead of f [] = [] and f (x:xs) = g x : f xs)
You get used to it after a while :)