Many damage bonuses aren’t shown on the sheet. That’s why the numbers become irrelevant after lv 70.
An example, +%element damage. No matter how many you stack, they won’t increase the damage number on the sheet. (But they do increase the damage while you attack.)
Most (almost all) of the legendary/set bonuses, and some magic affixes fall into this category.
Actually, only few affixes (e.g. critical chance and critical damage) are calculated into the sheet damage.
See the “Meaning of Diamond Icons on Item Detail Sheet” section of [Wiki] Acronyms - The Definitive List plus Definitions! to learn more about the meaning of the diamond icons of the affixes.