Because no matter how much you nerf her numbers, her mechanics ARE FUNDAMENTALLY FLAWED.
Being outranged as an ADC vs her is infuriating considering she has cc, stealth, heals, and a global ult on a relatively short cooldown with pinpoint accuracy.
Nothing pisses me off more than being unable to return fire to an ADC as an ADC late game. It is stupid. It feels like an insult on top of injury. She is played in literally every role but support now. People are abusing her overloaded kit and it feels like riot has been studying the CertainlyT playbook of "WHY NOT" in kits.
Her passive is what older champs have as ENTIRE KITS.
I don't want to spend the next three years giving this person the yasuo effect. Just remove some key features. Just like you did akali. A good start wouild be removing the self healing aspect of her Q and moving it to hitting a champ with her root. This makes it so she is rewarded for skill and not "lolz my kit."
Another thing would be to MASSIVELY lower the hitbox of her ult and increase the cooldown to Karthus levels.