This rather mixes simpler/more difficult and shorter/longer as equivalent - even interchangeable - aspects of writing. But these are not transitive: shorter is not simpler, nor is simpler (i.e., more understandable) necessarily shorter; similarly, a longer piece isn't more difficult simply by its length.

Writing is hard; writing clearly - more understandably - is harder yet. Writing precisely, which would link some concepts of length/wordiness directly with understandability and clarity, is the hardest of all.

"If I Had More Time, I Would Have Written a Shorter Letter" - Blaise Pascal