Too simple
Even for my basic circle spinning flashes, I added something to keep the reader attracted, such as decreasing the spinning velocity to lower, hence making the circle roll and fall. I can understand why you submitted this flash, so I will provide suggestions for particular areas of improvement for a simple animation.
The first thing that degraded the overall score of this flash was the resolution. That is, the overall size of the flash. A huge area of emptiness with a single focus (the spinning circle) lowers the depth of the flash and you must be sure that you are using the correct resolutions in such flash. Make it 200 x 200 or even smaller, depending on the size of the circle.
Other simple methods of making effective simplicity is to add shading or even a shadow, which would engage the viewer. Through these simple methods, the viewer would be more inclined to watch the flash. As I have suggested in other flash, a background would also be useful.
I hope these simple suggestions will stay in your mind. Good luck for future flash.