"Aang being neglectful makes no sense they did him dirty," If I have to repeat myself for 10,000 years on this website by Raava I will do it,
A) He was never neglectful in the actual legitimate sense of the word. Neglect is actual child abuse, not missing your kids' soccer games or not taking them to the beach and shit, (well, it can present like that... but listen, my point stands that;) I think people are way too quick to be flippant throw that word around, in this context and in others.
B) It was mentioned in the show that he was too busy with his "duty" and being the Avatar to spend time with his family. "But he always had time for his precious little airbender." Implying: Aang felt forced to spend his allocated time with Tenzin on his training, probably fearful that the only airbender after him wouldn't know enough to be a true master, and teach ensuing generations. He was not, perhaps, consciously eschewing Kya and Bumi from his vision of legacy altogether, but instead failed to balance his priorities with his children.
This paints a pretty realistic picture of Aang. Worked to the bone and full of baggage. A guy like that is gonna fuck up SOME time.
It's maybe not the most comforting idea that Aang would overlook teaching his other children and making sure they felt included in his legacy, because he got tunnel-vision or lapsed into ignorance, but it's certainly interesting. It's supposed to raise questions for the audience. That's what good TV does.
Is everyone capable of accidentally hurting their loved ones? Am I? Are my parents? What do we do when our heroes disappoint us? Can we find value in our disappointment? What do we constitute an irredeemable failure of morals? What does redemption mean to us? What does legacy?
This is why people don't like TLOK. Instead of packaging easy, warm, digestible answers to them about their favorite characters and the state of the world, it instead asks, "what if you had to think about everything a little bit and figure that out for yourself?" And wow, some audiences do NOT like that question.