In Defense of Kataang: A Misunderstood Relationship that works
Ever since I've been in the Avatar fandom, I have often seen and heard a lot of fans who either dislike or just straight up hate the relationship between Katara and Aang for reasons that are ridiculous and that don't make sense; it's "Hero gets the Girl", their relationship is "forced", "one-sided", that Katara treats Aang like a "brother" or a "son", that Aang doesn't view Katara as a person, just an ideal version of her, and that Katara never shown her romantic feelings for Aang throughout the show until the at the end of the show.
But do you want to know another that's most of these things and it's non-canon? Quasme; the relationship between Quasimodo and Esmeralda from Disney's The Hunchback of Notre Dame, a ship that most people, even to this day, want to happen despite the fact that it's obviously one-sided and that Esmeralda doesn't own Quasimodo anything, even though she was the first person who shown him compassion, never judged him for his looks, and Quasimodo saving her in the climax of the movie. Anyway, back to Kataang.
The age gap argument doesn't make any sense to me. Like, if Katara was in her mid to late teens and/or Aang was younger, then I would understand where fans are coming from. Katara and Aang have a 2 year gap, which can also be argued for a 14 year old and a 16 year old. And the "Hero gets the Girl" statement also doesn't make any sense either. If that were true, then Aang's only goal and motive is to win Katara by performing heroic acts, and Katara would only exist as a love interest with little to no personality who's a good looking prize for the male character.
In the words of Shadow the Hedgehog from the 3rd Sonic movie that came out nearly a year ago;
"She's not a prize to be won."
Katara isn't and never was a prize for Aang or anyone else. She's written as a character with a fleshed out personality, a character arc, ambitions, hopes, dreams, and a lot of emotions. Katara is very outspoken, is compassionate, but doesn't take anyone's bs, fights back against injustice and sexism, can take charge in situations when needed, is the glue to keep her friends together, wanted to learn waterbending, became Aang's waterbending teacher after becoming better at waterbending herself, and is willing to help others in need. Basically, she isn't just a love interest. She's a strong character who happens to have involvement in romance, but not to a point where it slowed her down or downgraded her character.
Also, Katara doesn't treat Aang like a brother or as a son (like, EWW!). She acts maternal to almost everyone, but isn't completely mature all the time herself. She didn't like-like Aang at first. But as the show went on, she began to develop feelings for him. The way Katara shows affection for Aang is something that she doesn't show to anyone else. She kisses Aang on the cheek several times, she was the one who suggested that they kiss while they were trapped in the Cave of Two Lovers, jets jealous when Aang gives attention to other girls or the other way around, and is extremely protective of him.
Katara got with Aang not because he's the Avatar or that he saved the world. She loves Aang just for being him and it was the right time for her to start a romantic relationship with him. Aang's feelings for Katara initially started off as puppy love, but as the show went on, his feelings for her gradually grew into genuine love. Aang is patient with Katara, he helps her have fun when she needs it, is very supportive of her, and he allows her to make her own decisions.