Item stacking invalidates the idea of class/origin bonuses

Why would I go knight or guardian when i can stack and be more tanky? Why would I go glacial or yordle when i can stack on and stunlock you the same way / make you not attack me, while not being punished by using all my units? Literally every game I see a double locket and/or a double shojin on someone. This game should NOT have a "meta". And yet it already does.