So I was thinking about how ATLA inverted the favored sibling trope -if u can call it a trope-. Like usually in fiction, it's the older sibling that is the favorite and the younger one is kind of the underdog. And then I realized that they didn't only invert it they also subtly executed the classic version of it. It's never said explicitly but in the one scene, where we see Ozai and Azulon interact with each other, it is abundantly clear that Azulon favors Iroh - his older son- and completely dismisses Ozai. Ozai is the one lacking, Ozai can't do anything right in his father's eyes.
And now we go one generation further, Ozai is now an admittedly terrible father to two children. Zuko and Azula, and who does he favor?!
Of course he does, Ozai heavily projects on both of his kids. He goes the extreme other way and puts the same abusive pattern on his own children, just reversed.
- Iroh himself btw never has the opportunity to develop that pattern, first of all because he only had one child, and second of all because he was the one who got the at least somewhat "healthier" dynamic with his father and probably his mother, if we go with the theory that Ilah died in childbirth.-
Because he sees the exceptional prodigy of Azula as himself, the second child, who in his narcissism is the better option. Who he can form to be the perfect successor of his legacy.
And in that way of thinking he treats Zuko, his older child with the same neglect and dismissal as he was treated as a child. He himself does not realise it, but he creates in that way in Zuko a kind of distorted mirror image of himself.
With one difference. Zuko has his mother and his uncle to teach him compassion. Not only that but Zuko himself is someone who as a person has a strict honor code he follows. (See 41st division).
Zuko is with that in mind, not just a reflection of Ozai but also a WEAK reflection from his perspective.
Which puts us back to the reason of, why he burned the face.
So in conclusion did ATLA not only invert a trope, it also used it to develop a unhealthy family dynamic and create a realistic picture of the cycle of generational trauma.