I don't know if it's intentional or a way to create drama. However I can see how some of the dysfunction can occur. Firstly, it could be the kids feeling like they are trapped in their parents' shadow. You parents saved the world. One parent was an Avatar whose job was to keep the world in balance. You dad was the last known airbender; then you're the last airbender. I can see Aang unintentionally playing favorites with Tenzin due to the airbending connection. All things airbender rested on little Tenzin's shoulders until his children were born. Of course we haven't heard about Katara's side in all this. To be fair, Aang wouldn't know much about families and conventional parenting since he was raised by monks and not his real parents.
Toph obviously was a rebel and thought living her life the opposite of how her parents tried to raise her didn't completely work out with Su and Lin. Based on spoilers as to what caused the rift between them, I can understand Lin's distance. In their case I also think it's about lifestyles and desire. Lin was hurt when Tenzin left her for Pema, and perhaps she was jealous that her sister had the home and family she might have wanted but sacrificed for her career in the RC police.
We don't know what Sokka was like as a parent, assuming he had children at all. So far there has not been any mention of cousins in the Water tribe for Tenzin's kids.
Indeed! Katara taught her well.
I loved the whole look of the Metal City. However they are asking for trouble by mentioning it was the safest city in the world! I liked how the whole goal in the culture is to encourage people to reach their potential. I am curious about Su being set up to remove the Earth Queen. There is no love nor loyalty to her and in her opinion, she's not part of her world of progress. Verrick's appearance also makes me think something is going down before season's end. I wasn't expecting to see him so soon, but with him in the mix, anything could happen.
No one seems to have mentioned this, but since Opal is an Airbender, does this mean she never was an Earth/metal bender? That on it's own must have been difficult considering the rest of her family are. I can't remember if it was mentioned if Su's husband and eldest son were either - only that they were architects.