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Good animation is all about patience. There is also the difference between being bad at drawing, and drawing lazily. If you take your time, your drawings will be better. There is no doubt about that. Spend more time on each drawing and each frame, and you'll have something much more pleasing to look at. Flash makes it easy to change your brush size to something more manageable, and there is a pressure setting you can use with your tablet. If your drawing is jagged or rough, either erase and redraw the lines, or use the Selection tool to clean it up. If a drawing looks bad, don't just accept that and move on. If you're drawing something like a building (such as the one in your video) try holding the shift key while drawing with the brush tool. It will automatically allow you to draw horizontal or vertical lines.

With your voice acting, try to avoid having moments where you can actually hear you breathing into the microphone. As a general acting tip, make sure that you deliver each line with motivation. You aren't saying them just because you have them written down, you're saying them because the characters have real reasons to say them. Think about each line before you record it, and ask yourself why the line needs to be said. (The answer will never be "because it was written into the script")

(If the script is just absolute nonsense, and the lines are only being said to be such, then none of the second paragraph matters or applies.)