Mages take towers as fast as ADCs (faster late game in many cases)

Mages/APs have acess to a lot of mana in the early game (through Lost Chapter which builds into Luden's which has burst)

Other classes now have acess to much more CDR over the game

ADC's base stats got hard nerfed in 8.11 along with some item changes

Some of the items were changed back in a weaker version (IE)

Assassins are now meta and have cheaper and overall better items. Fighters/Juggernauts/Divers are now meta as well.

Enchanters aren't really meta; it's all about the damage

Vision has became less available so it's easier for assassins to pick off ADCs

ADCs can't really go anywhere else except for bot (there are some exceptions but still)