About Zed Ult and QuickSilver Sash

Patch 6.9, I believe, was when the change was implemented, where QSS became only able to cleanse CC effects and not non-CC debuffs like Zed's ult and Fizz's ult.

I still don't get it srsly. Why would Riot even consider doing something like this? I am not talking about Zed, I don't care about Zed because my mains usually counter him hard. I am talking about QSS in general, item was completelly fine, there's nothing wrong with an ability to remove a debuff. I've never had any problem with ADC removing my debuff or CC with QSS because they sacrificed a lot of gold and damage to get that item so they can save their lifes.