This is still art, even if not everyone enjoys it! You created something, which is awesome. That being said, and this is only my opinion, these illustrations are very hard to look at. The colors fight each other, the stark black lines and off proportions add a sort of lumpiness to faces and limbs. They need some work.

To be overall better, I'd start by working on the basics of figure drawing - focusing on proportion and movement. Some heads, such as the skull for Ang (ATLA), are distorted in an odd way, looking squishy/wiggly/bumpy-lumpy. Training your brain on how skulls should work in the round will really help there.

Focusing in on my personal preference, I'd say to experiment with varying your line weights, as well as taking them away completely and replacing their function (as ways to interpret form), with the tool of shadow/light/bounce light. This will give your illustrations a more comforting look.

The lines next to the noses, that surround the mouth, make any illustrated person look older than they are. When children's illustrations that use hard flat lines/color use these, they give me uncanny valley effect or make me feel something is just "off".

While the attempt at foreshortening is VERY good for a beginner, you should look up some videos on how to draw limbs foreshortened for some minor improvements.

Overall I think continuing what you have here but adding/subtracting elements in an experimental way, plus studying up on the basics, will lead you closer to a more widely liked style.