Welp, in the newer games population only translates to science pretty much. Shame.
I did like being able to conscript units with that crappy grassland city 5 miles away that I placed
I'm not sure what you are saying here:
In
Humankind, your city gets 'Slots' for Money, Industry, Science, and Food from building the various types of Quarters: Market, Makers, Researchers, Farmers Quarters, respectively, and you can fill any of them with 'Population' for extra Points in each. Population and Quarters/Districts then, translates into the basic currencies in the game, and you can move the Population points around at will to 'emphasize' what you need most at the moment
On the other hand, and where
Humankind is, frankly, Head and Shoulders above Civ VI, the various systems in
Humankind actually work together. So building a bunch of Districts/Quarters to scoop up the points/Population costs you Stability (-10 Stabilty per Quarter in most cases) - but later in the game, you can build Commons Quarters that Increase Stability. OR you can from nearly the start of the game, build Garrisons that increase Stability (This isn't a Unit as a garrison, but, basically, a Fortification to overawe the citizens and keep them in line) and then other Infrastructures like Public Fountains, Aquaducts, Sewers that increase Stability ("Amenities" ya gotta call 'em). Civics choices can change Stability. Diplomatic Actions can change Stability. Luxury Resources exploited or Traded increase Stability - so declaring war on a Faction you are trading with can suddenly drop the Stability in your cities, which could be Disastrous if Stability is already less than perfect.
There are other Infrastructures that increase the number of slots in the various Quarters, or the amount of points of the various Currencies you get from them, so you can (and should) constantly switch back and forth from building Quarters for Slots to building Infrastructure to 'enhance' the Quarters to building 'special' Quarters like Commons and Fortifications that offset the Stability loss from building Quarters. It is an extremely dynamic and integrated system that for much of the game keeps you constantly thinking about your next action in regard to each city to maintain them and get the maximum benefit from them.