the subject you chose don't particularly provides problems for pixel-art it rather provides problems regarding to posture, anatomy, deep space (aka foreshortening), weighting.
Main problem I see here with the pose is that the angle of the spine suggests a really deep bend ribcage.
If you bend your ribcage forward, you usually shift weight to your butt in order to counterbalance the weighting.
In order to get the spine that low the upper legs are to short to support the weight shift, which means you would have to use your hand in order to support your weighting.
The hand of the skeleton nearer to the ground however seems to perform a quite weird grabbing movement.
However if I just interpret it how you have drawn it it seems more like a quite static luring position, wiothout thinking of the weight.
Regarding to the weigt distribution I lalso could interpret it as moment-shot of an inbetween action to get a dynamic image there are 2 possibilities
-the pose was stable before and the skeleton tries to stand up.
-If it goes in the other direction and the skeleton makes some kind of dodge movemen and let's itself fall down
For both scenarios you won't move your arms that way.
With that said, I think it's easier recognizable that the pose provides some challenges.
Especially if I look at the arm joints, the legs and how the forms foreshorten there is a lot of inconsistency.
Only thing which would help there at a fast pace is to get an exact pose reference (best of a skeleton)
Thing which would help there in general to overcome your weaknesses, but is of course really time consuming and needs a lot of practice would be to thousands of quick gesture drawings to understand the principles of weighting and foreshortening. Next thing on top of that would actually to look up anatomy and try to learn which bones the human body has and how they look like and to which maximum angles the joints can move.
Actually I tried to find out what your pose looks like and did some quick sketches based on your drawing andtested out what would happen if you lower the spine ormove it in a more vertical position. If you are illustrating any human spending lots of thoughts on the pose is usually the first step. Once you know what's going on and how the movement is you can construct the forms on top of it.
Here i just roughly threw in some forms, that you have a bit more than highly abstract lines and can get an idea what I tried to change. The red mainly supports thoughts on weight.
