This is a very striking piece. I agree that the show could have done more (they were constrained by stupid Nickelodeon expectations). It is true that they needed to leave their lives, but then again they are kids, they find it a bit easier than adults. Also, when it really matters, it is easier, perhaps better to leave home to go save the world, even if you didn't know it at the time.
They didn't make it seem like a big deal that Katara and Sokka packed up their lives and left the only place they knew to make a journey and help a friend. This is a fine tribute to that aspect of their lives. It looks lovely, with the shadows and soft light and colors in the sky.