That’s one of the weirdest things I see that’s so prevalent in Zutara takes. Aang and Zuko are close friends in the end. Aang’s offer of friendship, starting early in S1, his pacifism, his ability to reach beyond his culture and connect are all vital to Zuko’s entire redemption arc. It’s as critical, if a bit less present, as Iroh’s. Aang is the first person that’s ever been in a place to offer Zuko friendship just for friendship’s sake, and when Zuko is finally able to accept it and offer it back, it’s huge for Zuko. Zuko and Aang’s evolving relationship is the foundational structure the show is built around. (That and the evolving Aang and Katara relationship, but we won’t go too far that direction right now.)
There’s also this weird fascination with making Aang a bad person and Mai a bad person. Why? For fanon shipping reasons, you can just have Mia and Zuko break up (or follow the stupid comic plot on it), and likewise Aang and Katara are young. They can split up. Really, anything approaching canon character takes is going to involved Zuko having a long conversation with Aang before proceeding with anything with Katara. Zuko’s sense of honor is way to high to get involved with a friend’s ex without a conversation first, even if it isn’t technically required. (Don’t even get me started on the nonsense of Zuko cheating with Katara when she’s still with Aang. Zuko would rather throw himself in a volcano than dishonor himself like that - don’t think Katara would either, but man tell me you don’t know anything about Zuko!)
I see other fanon ship takes that don’t see the feel the need to demonize other characters for their ships. They just go have fun with it. There’s something really weird about a sizable slice of the zutara community, and I do assume it probably goes back to 2008 (or earlier, given how obvious kataang is as the end game from early in the series). I only watched it 4 years ago, thanks to covid lockdown, so I never got to experience it live during the original run, thank god.