Simple kits cause so much change purely because they can abuse things because they are stat checking other champions. These cause items and runes to be balanced manly towards the point that simple champions can't abuse them. Like remember when devourer existed and how all simple champions that abused got the item nerfed and eventual removed from the game. Some champions include, Master Yi, Pre-Rework Warwick, and Xin Zhao before his minor update.
Loaded kits rarely lead to item and rune nerfs mainly just champion nerfs which IMO is better to do than to consistently change both and effecting the whole game that much more.