As i see it, the problem is that there is a gap in the 3/4 of the pitch.Last year we had this problem too.
Think about it.
One of our attackers receives the ball with his back to the goal, outside the penalty box.He can not do anything as he is marked.He passes back to one of the central midfielders, then the ball goes to the flanks.And the best our wing backs can do when in possesion is an average cross to the box.
Remember Marchsio's goals against Milan and Inter in Conte's first season.They came through team play and combinations outside the oppontents box.Now the players don't even try this.