
Rapunzel has the closest look clothing-wise, but there's a distinct dark skirt and lighter top. Our eyes naturally seek out the highest point of contrast in an image, and for characters that should be the face. Rapunzel's hair has bright gold highlights, again pulling the eye to the face.
Edit- she also has two vertical lines all the way up her dress, again guiding the eye around the design and upwards.
Now Esmerelda- who is much closer to Asha's skin and hair, but we have a bright white tunic, not to mention vertical lines in the corset, and the curved skirt line, all of which guide the eye upwards to her face. (In some frames her hair tie also works as a brilliant guiding line)
Our brains like contrast, and they like to follow visual lines. Asha's character design doesn't make use of either, resulting in a bland appearance.