The total lack of structural drawing.
Actual artists start a character by drawing a skeleton and shapes to give the character proper proportions, and then draw the actual character above that structure.
The person drawing this princess obviously doesn't know structural drawing and started by directly drawing the character outline.
The end result is a lot of small mistakes that, added up, make the whole drawing feel wrong (and flat): the whole arm is too long, the forearm itself is too long, elbow don't bend like that, the shoulder on the left is too high and doesn't align with the neck line, the line on the left of the torso goes nowhere, the fingers are too short for the hand palm, etc, etc.
You can even tell that the person drawing this started with the face, then did the torso, and ended with the arm and the hand.
There is a reason why professionnal artists all have anatomy books.