Yes, defending is very important of course.But do those fullbacks do that every weekend? There are 20 teams in the league, each gameweek will see a FB contribute towards a goal in some way or other.
I like my full back chipping in when he can but I also agree that defending is his first duty. Anything else is a bonus.
But what everyone here
( don't think anyone has mentioned it) are forgetting is how important fullbacks are in Klopps system. It was the same in Dortmund with Schmelzer and Piszczek.
Why is Milner thriving at fullback? Because he's allowed to bomb forward at will. So we need some sort of contribution from our fullbacks. They're extremely important to our attacking play.