Neeko and Qiyana honestly aren't that bad there's reasonable history in thier lore for why they are like that.
Neekos first language isn't the main language of Valoran/shurima, heck on her old island she didn't even have 2 talk; her people just communicated psuedo-telepathically my exchanging parts of thier sho'ma (spirit) kinda like ants with pheromones. She talks like that bc she's learning the language. The reason she's lesbian is bc when she shape shifts she takes on the other person's aspects and sho'ma, she kinda becomes them and as a female she's more comfortable with the female anatomy.
Actually your not supposed 2 even like Qiyana where she is in her story arc right morde she is an unforgivable villian who is completely self absorbed, and she fills the niche of probably being the most arrogant human characters. She may have her "reasons": being incredibly talented royalty that normally nvr would b granted anything if she wasn't taking action. But she's legitimate designed to not be likeable atm.
Yuumi is a cat, either u like that or u don't. But that isnt a flaw in her character design.
Zoe's an irresponsible preteen given the power of an aspect, ur not really supposed 2 like her either, still not a flaw in her design, sometimes kids aren't enjoyable personalities.
Kai'sa is the only one who is objectively a flawed character design. Basically her whole design suffers from a lack of direction. In terms of her character they got stuck between Samsus, Laura Croft and Kerrigan for inspiration and didn't pick a path 2 follow. This is why she has no interesting personality. They had 2 fill the empty space with something.