You're only right to a point. Atmas Impaler was broken, maybe still is. They nerfed it significantly, and now people should be more creative about maximizing their builds.
But smart players and teams build around *each other* to maximize team potential, and Atmogs is a solo mindset. Plus, in early days tank-teams would roll. Their was just no way to stop them pushing 5 middle lane and ignoring your damage. You may notice more squishies have higher CC and utility than in early days...
And resistances don't amount to nothing. You buy armor, they have to buy armor pen. Same thing as you buying bulk, them buying damage. The whole game's a balancing equation. Anyway if you hate armor pen, buy a thornmail and make them pay in extra damage returned.