The micro of many cities is there in 2 cases:
1. You are going for Domination, but in this case you don't need production after some point.
2. You are playing on a very low difficulty(srsly, I play on Immortal and don't get more than 12-14 cities - and when I invest into an army to take 2-3 cities from the opponent, I win later).
In other cases, you just wouldn't have that much micro, but the existence of such metropolises could make a science victory much easier(suppose you have 3 cities with 60 prod in each. Before lasers, you can only produce 1 project at a time. With metropolises, you're going to make it 3 times faster).