I had a conversation with a Kataang guy, he said Zutara to him is the same way we Zutaras see Kataang, stating that Zutara gives off more of friendship/sibling vibes than lovers.
And it just comes to show that if you only put Aang's best interest in mind, Zutara couldn't happen because Aang just had to get the main girl. Of course, this is following the thought process that "main guy gets main girl" but I firmly believe that it would have also done Aang some good if he ended up with someone else. BUT if we took everyone's best interest, Zutara would have been the pair to go with.
Going back to that conversation I had with that Kataang, it was obvious he wasn't thinking in the perspective of Katara/the woman, and what she needed the most, which isn't a guy like Aang. Girls would get it, most of specially the "mother of the group" and though Katara isn't the eldest daughter she does have that archetype to the whole Gaang. Her archetype doesn't usually end up with a guy like Aang, both theoretically and in real life. Another point to the "Kataang" thing feeling so forced.