Perhaps as you advance through the levels of the civilization there could be checkpoints that change the way the game feels. During the stone age we are only managing 50ish nuggets, so we are responsible for happiness, food, water, medicine. Maybe when you reach 100 or 200 nuggets we can get a "congrats you're civilization is advanced enough to manage it's own food/water needs" etc. Then we can focus on power construction, road building instead.
Then repeat through the ages and those get taken care of later and we can build rockets and rocket stations. That way when we have multiple planets our people can take care of their basic needs all by themselves and we can focus on the space travel, wars diplomacy.
If you go this route, as you scale up then you don't need an AI running 1000's of nuggets and multiple planets on all the planets all the time, production could just be calculated for the lower level stuff and then render it as you zoom in. Go to a planet that is having an issue and solve it with diplomacy (overthrow the government!) or war (build nukes) while you other planets continue producing without rendering individual moving nuggets. Instead of a nugget list you would have a planet list with attributes like nuggets perhaps.
Seems like a viable way to scale up from a small town to a galactic empire and keep the game interesting. The powers could scale up as well from "repair building" to "terra form planet" etc. (Or destroy planet if you so desire