-For one thing, pointing your racquet back does not get your shoulders turned.You can easily point your racquet back while still facing the net. Instead, think "unit turn." For proper technique, your whole upper body should be turning together.
In the pictures below, notice how both Federer and Agassi hold on to their racquets as they prepare for the ball
-Another issue is that your racquet doesn't have any momentum behind it to help swing aggressively at the ball. In this video, notice how Fernando Verdasco's backswing is smooth and one constant motion. Once he starts his backswing, his racquet never stops moving until the end of the stroke. If you use the "racquet back" theory, you will have to swing at the ball without the added momentum of your backswing, making it harder to swing at full force.
-The last problem with is that you don't get your non-dominant hand stretched out across your body. This arm acts as a measuring stick, helping you maintain proper distance away from the ball.
Hope this helps. Remember, don't think "racquet back," think "unit turn."