What is up with tanks??

I have been playing a ton of top lately, and I usually play Camille. And I don't know if its just my champ or if its like this universally, but it seems universal and I need someone to explain this to me because Riot finds it balanced and I have no idea why or how, and maybe someone does. Every time I lane against a tank like Nautilus, Sion, Malphite, Garen, Or anyone in that class, I always find it impossible to win lane against them, because they build pure defense and still out damage you????? How is it balanced for someone to build pure armor or MR, ZERO offensive items and out damage someone who is building PURE offense? I don't understand how this is balanced and what the counter play is? I might be missing something really obvious or easy but I've tried everything, I've taken press the attack, conqueror, Comet, Everything that is considered meta on Camille, I seriously don't understand how it's balanced or viewed as fair and I'm hoping I could get an explanation... Thanks.

EDIT: I just now found out that they're adding a new item named Atma's Reckoning, which is going to give tanks even MORE AD. WHAT??