I've noticed, sadly it's the world we live in. Women in everything and in real life always get reduced to objects of some sort. I hardly see anyone treat any woman with respect. Shitty really.
But anyway, most of the girls in the series (kairi most of all) hasnt been repected by the writers and creators themselves. As I stand on what you call "a kairi hater" I'll do what do best. Kairi hadn't had much screen time. Yeah she does do some stuff, but shes hardly ever on screen and it kinda over shadows it the stuff she has done. You have to look deep and read the manga and shit to find an actual character it's not just right in your face like the other three girls.
Now with xion, tbh the only hate I see about her is that she's a Mary Sue and gets in the way of the fandoms most popular ship, akuroku. And that's bull. Last time I checked Mary Sue ment someone who perfect all around, someone who everyone likes, someone who's beyond pretty. Trust me xion is not perf. In canon she had many flaws. I'm not gonna touch that because I don't feel like doing all that. But xion is not useless, I can make a list but I'm lazy.
Namine, yeah namine is kinda selfish. But she was forced. Most things I seen that shits on namineis the things she has done in com and not after. Ppl remember the bad she's done an not the good.
Aqua. Now I don't even get it, yeah aqua is a babysitter the mom yeah. But no one says nothing about that from what I see. It's always about her boobs and body and shit. And tbh I hate it so much. I love aqua with the life of me. I hate hate hate when people reduce her to like....that. Aqua has done a lot and will do a lot. In my eyes with aqua it's just people making her their fap shit. Which I'll say again I firetruckING HATE.
Excuse any grammer and spelling, my brain isn't awake yet.