It's that Riot made her so dummy thicc that her thighs are unrealistically out of proportion EVEN FOR A GAME.
Like, Fuck, you can quite legitimatedly put a 3rd leg in that space from how far away her thighs are from each others. We get it, you wanted to introduce a legal thick petite with a stuck up egomanic attitude. That in itself is fine.
But please, at least make the proportions believable. Also look at her torso to hip ratio. I gotta believe that something went wrong with her and she survives through ancient and powerful magic because jesus christ this is such an eyesore.
And note, this is the most frontal picture of her that I could find from the clip. Nowhere else does she stand as straight up while facing into the camera, so if this doesn't convince you then IDK what will.
Edit: After some critics both good and bad about the post, I have additions to write:
1. Yes, some champions do get disproportioned so the bird's eye view works out. But these are kept at a bare minimum or are angled in a way where you have to stare like a sicko to notice it, like Darius' arms stretching to 2.5x their length during his ultimate dunk. But, none of them are quite as brutal and visible as Qiyanas. Her trailer has some rift gameplay and even there you can notice it extremely well.
2. The issue has little to do with her attractiveness. Her beauty isn't a problem, it's that it doesn't fit with her thematic at all. For someone who's supposed to be from the jungle, she has quite a modern haircut and quite the civilized set of clothes, for example. Hence why her hair has been a critizised point so far.
3. Have you looked at her torso? From the chest down to the hips, shes a literal triangle. Fuck, I actually used paint and drew a triangle just for this point, and it's a fucking perfect fit.