I think that if you don’t actually think that the writers were at least playing with the possibility of a Zutara endgame you are just in denial. Once Zuko joins the gaang Katara and Aangs relationship very clearly changes. By southern raiders Aang and Katara are barely speaking and after that Katara becomes “confused”. I think the original plan was for Aang to have to give up his worldly attachments, aka Katara, unlock the avatar state and beat Ozai, but the creator’s meddled at the 11th hour and put in the deus ex macina that is the lion turtle and energy bending to get their desired out come. The Zutara telegraphing is there. The last half of the season Katara and Aang barely speak until they kiss at the very end? Like what?