I'm sure Aang was a good dad, or at least tried to be good, it is just difficult to be the child of a famous father. It is like if a father is a famous mathematician and one of his children also shows an aptitude for math, his other kids feel jealous and neglected because there is a special world that they cannot take part in. As for Toph, I feel like her actions fit with her personality. I think for Toph being a police officer was more about "fighting the bad guys" than trying to uphold the letter of the law in every instance. The same qualities that make her endearing as a rebel make her lousy as an authority figure.
My friend put it this way:
He was not a shit father on purpose, he just was trying to sort out the world and pass on as much of his culture as he could before he died. He still felt guilty about running away when he was a kid and not saving the air nomads :\
I think this show requires you to really step back and look at the bigger picture with a lot of these plot points. They are showing us very brief chunks of moments, and then you just have to go from there and put it into context to everything we know. I agree that Aang probably felt a lot pressure and a lot of guilt about what happened to his people. It makes sense that when he had Tenzin, he had to pass on everything he possibly could (as well as training the air acolytes), because he wasn't going to live forever. And if Tenzin wasn't a good air bender (or god forbid died), then there people would be lost forever.
That's a huge burden. If you put that into context to how it impacted him as a father, I think it becomes a bit more understandable. That doesn't mean that he wasn't a shit father. Clearly he should have been there more for his other children. But it at least puts a little more context to the situation.
I still go back and forth on using flashbacks to tell future plot for characters we know really well. Because it does cut out everything that came before, and we have to just accept any changes the characters might have gone through as people. The only way to try to do this is to take what we knew about them in the past, and try to apply it to their actions in the future.
But for me, I still find Toph kind of a confusing character (in regard to this storytelling). I mean I GET why her actions make sense. Toph was someone that didn't like being told what to do, or who she had to be. She rejected this idea that she needed to grow up and fulfill her family's wishes. So it makes sense why she would have kids and then give them complete freedom to be whoever they want to be.
I just struggle with how Toph came to be Police Chief (the person she comes to be, that wants to accept that position). And I just feel at the point that Toph is the person to take that role, I just wonder why she would 100% hold on to her old beliefs (such as allowing her one daughter to run free and be a criminal at the expense of their family). Toph was always bossy, and wouldn't let people fuck around with her. So while I get her belief is that her kids have the right to be who they want to be, I just have a hard time imagining Toph putting up with that shit (to a certain point). Especially if shes changed as a person to the point she would take up Chief of police.
THAT is my issue with her character (or rather, why I think Toph is a terrible person). I don't think it's acceptable that she gave Lin a cold shoulder and was dissapointed in her for wanting to be like her mom. Again, I can understand why Toph felt that way initially. But to hold on to those feelings and put that off on Lin is completely fucked up. Especially when she allowed her sister to run all over the family.
Then again, I guess some people are stubborn. *shrugs*. We see that with Tenzin, who still has trouble letting go. Maybe Toph was just someone that couldn't accept her philosophies weren't working, and she was being a shit parent.