The main problem is the same problem that most people (including myself) have when they start out and decide that they're going to draw cartoons.
You really need to study real life before you're able to make it work.
Here's a small remake from me. I put fuck all time into it and fuck all work, but you can see that I made a preliminary underlying sketch to judge the figures and see where I wanted my lines to be. You honestly do need to work on real life before you're able to judge cartoons because it gives a sense of weight and volume that is necessary to know before anything else.
What I've done isn't good but it has more 'feel' to it in comparison.
