Mercury Treads Changes

I don't usually post on the GD, but I felt like something had to be said about this.
I don't understand why the only real counter to CC in this game got nerfed so heavily. Who on here was complaining about mercury treads being too strong that Riot's balance team decided to take an axe to the tenacity on them by dropping it from 35% to 20%. Zephyr was removed, and there is no way to go 12 points into Resolve to get Swiftness when you see the enemy team stacking CC. I just don't understand the logic behind this change. Somebody explain it to me?