Honestly, Zutara never really appealed to me, and there is a reason for that. If you are not interesting in hearing my opinion as to why I don't like this ship, then DO NOT read. If you are interested, then feel free to continue reading this. I will try to say this in a way that doesn't seem so rude, but keep in mind that I am just sharing my opinion.
I took my awhile to realize why I didn't like Zutara. I tried so hard to ship it, but every time I tried shipping it, I was left off frustrated. The ship made me cringe so badly. After some time, I figured it out why I didn't like the ship. It was because of the good girl and the bad boy trope.
If Katara where to be with Zuko (the bad boy), she would have to reject Aang. Too me, it seems like the stereotypical thing a heterosexual girl would do (I am not implying that Katara is straight, but the ship still gives off that vibe). My point is, it makes me cringe to see Katara reject Aang just to get the bad boy. Now I know a lot of Kataangers say that if Katara rejected Aang, then Aang would be sad. I will admit this argument is lame (even though I am a Kataanger) because Katara has her own feelings as well. She is allowed to choose who she can be with. That doesn't stop Zutara from being cringey though (at least to me).
If Katara where to be with Zuko, I would respect that and accept that it's canon, but that wouldn't make me like the ship. That wouldn't stop me from finding it cringey. I honestly see the appeal of Zutara, but as a queer person myself I would much prefer Zukka and Kataang (I'm not a hard-core Kataang shipper, but I much prefer it much over Zutara).
Zutara also gives me Jetara vibes. I was cringeying so much when Katara had a crush on Jet. I know that Zutara isn't Jetara, and never will be Jetara, but you gotta at least admit that Jetara is kind of similar to Zutara. Although I absolutely hate Jet, and love Zuko (who is my favorite ATLA character). In that case, I don't think Zutara would have been nearly as cringey as Jetara.
I can also see why Zutarians might not like Kataang too much. I get that Aang might be a bit childish and annoying to Katara, so I could see why some might not like Kataang. If you're a Zutarian, keep shipping Zutara, I understand the appeal. I admit it, I really wanted to ship Zutara, but for some reason I just can't.
In conclusion, these are just my opinions. Feel free to share your opinions on Zutara, Kataang, or any other ATLA ships, but try to share your opinion in a nice and kind way. I want a friendly debate, not a war.