Caveat: This is subject to change, and not set in stone.
Bronze Age will be "finished"when you can grow from your first 7 citizens to an entire Empire. A dozen major cities, linked with trade networks, and a total population in the thousands. You will deal with the several races of local tribes through both warfare and diplomacy. There will be rival empires along your border, with which you can trade and wage war. Armies in the hundreds will clash on the battlefield. Charriots, spearmen, archers, and auxilaries pledged by friendly Maskling (and other) tribes. The gods themselves will take interest in your empire, as your priests invoke their favor.
TL;DR: Civilization and Dwarf Fortress had a baby, delivered by Factorio, and they named it Bronze Age