One of the most shocking changes in Patch 6.9 was to Quicksilver Sash. The item was retooled to only remove crowd control debuffs, not major single-target debuffs like Zed's mark or Lee Sin's kick. TSM AD Carry Doublelift is very upset by the changes and talked about why he hates what Riot did on his stream.
At first glance you might think this was simply an AD Carry being upset that the item was nerfed, but in reality his gripe is that making QSS fundamentally simpler lowers the skill ceiling to the game.
"There's just so many different ways to use QSS. It takes a lot of skill to use. I think it's really stupid that they're just making this item basically only work on a specific type of debuff, which is hard CC. It just turns into another cleanse."
Doublelift's belief is that the game is at its best when players have to use the most skill possible at timing their button presses. While the change to QSS certainly makes it a less viable item at top levels, it also makes it a much easier item for amateur players. The timing window is much broader and there's less of a risk/reward element to using QSS at the last possible second.
Time will tell how large an impact this has on professional play.