Okay yeah Kai'Sa needs a change in her kit
She's an ADC and Assassin. Which you may be comparing her to twitch but twitch doesn't have +100% increased movespeed and undetectable stealth that can be activated immediately in 1 button that also gives her bonus attack speed after it's over. It feels like I'm fighting Ekko but he also has ranged attacks and instead of ulting to save your life (because you have stealth speed and lifesteal for that) you ult to chase. Like Noct ult I guess?
But She's definitely doing too many things too well. I'm not saying nerf her damage, but her kit needs something taken away from it. Like the upgrade ability or the w's range.