Footwork is important in every point and every shot. You need to have your feet in the correct position if you want the most effective shot. If you do not get your feet where they need to be, then not only that shot will be a bad one, but then the rest of the point will not be good. Also, when you have your feet in the right place, then your shot can be more powerful and spinier. Then you can get your opponent out of position.
The second thing I want to show you is the way to have correct footwork. There are many different aspects to footwork that you must have. The first one is to always have your knees bent. If you do not have your knees bent, it will be so much harder to move your feet. Another important thing you need to know is where you last hit the ball. Most of the time the ball will be coming back diagonal from where you hit it to. So this will help you sort of predict where the ball will be coming. Finally, weight transfer is another very important thing. Without correct transfer of weight, your body will be off balance and it will ruin your entire game.
In conclusion, I believe if you work on improving those three areas of your footwork, your game will improve a lot, and will take you to the next level.