It might be a trivial difference, but I think it's an important distinction to say that the reciprocal is more true (probably what you meant anyway): Attention spans are the enemy of the modern world.

There's so much research that goes into user engagement Etc in order to control and manipulate the human attention span, I don't think it's fair to make it sound like it's the "attention span's fault" necessarily, when there's so many entities actively vying for it.