If you are hitting a ball from your own service line, you do NOT need to create pace to hit a winner.
Your position close to the net takes time away for your opponent to react, and a average backspin volley is a clean winner if the opponent didn't know where you were hitting it, and it lands within 2' of the baseline into an open court.
Do you ever practice your volleys? I do, sometimes. I stand AT my own service line, and even against top level 5.0's, if I volley to within 2' of the sidelines, nicely controlled deep, they can't get to the ball in time to hit a solid consistent shot. Those are controlled volleys I'm going for.
Positioning can take the place of ball speed, both your positioning and the positioning of your ball.