Maybe the most underrated responsibility for a wide receiver is to create separation from his defender before the ball ever even touches his hands. Of course, nothing is more important than catching the ball as a WR, but those who can’t get away from the defender seldom get that opportunity.
The NFL features some of the most athletic, quick, and technically sound people in the world playing defensive back, and their main objective is to keep the opposing team’s WR from catching the ball. If you can’t separate from these athletes, then you’re not long for the league.