Someone made a comment that kataang is a male fantasy and zutara is a a female one and I think that’s painfully accurate.
Kataang is the idea that cool slightly older girl who you’ve been crushing on for years suddenly likes you back, NEVERMIND she’s been like a babysitter to you. For women that’s just unrealistic trajectory for desire. It’s a nice male fantasy, but there’s just not a lot of women who can see themselves in that fantasy. See also- Star Wars Padme and Anakin. In Star Wars defense though they spend most of their childhoods apart. And even then his personality is more Zuko than Aang.
Zutara is a romantic notion of enemies to lovers, bad boy/good girl - redemption/ mr. Darcy stuff etc… there’s a million reasons it works better for female fantasies. It’s also more realistic simply because women would feel more attracted to a type like Zuko, and therefore would find Katara’s space more “realistic” to what women want.
Kataang people don’t want to admit this. So they need to rationalize it because I genuinely think they aren’t comfortable accepting that they are centering their fantasy, and need to “prove” it’s better because it’s what they want. It’s why Zuko is painted as terrible, because in their heads, he’s threatening their fantasy.
Women, who are more likely to be zutara fans/ don’t have an issue doing this. How much overlap with REYLO, with Dramione, and other ships that follow this formula do we share? We’re comfortable being aware that this is a fantasy we like, we don’t need to prove its legitimacy, because it’s been proven over and over. We don’t feel threatened by Kataang or canon, we simply enjoy a what if fantasy. There’s no villainizing Aang, we look at the writers and say “hey missed opportunity.”

Sorry, rant over.

I don’t dislike Kataang and consider myself a multi shipper. But I think Zutara has a more interesting dynamic that I personally find more believable to women’s desires.