Population being a completely worthless resource is one of the biggest disappointments so far in the beta. Why do the devs hate it so much? It can fix a lot of problems the game struggles with, and fits the setting nicely. What's more important in a post-apocalyptic world than getting the most people around?
I really hate the fact that currently positioning defines both food (which I can explain to a point, obviously terrain plains a big role in farming and herding, but it still needs people to do it), production (which is bogus, a settlement with one villager on a 4 resource tile works much faster than 100 people on a 2-resource one) *and* magic affinity (this is currently broken, upkeep-less enchantments coupled with high energy=instant research/development/production). Even taxes depend more on buildings than population. Now, because city position is so important, rolling a good starting position is absolutly crucial. Having your capital on a bad spot will cripple your early game. You can always restart the game if you want in single player, but in multi, it's impossible. I'm not saying that terrain stats are bad in general (War of Magic shows why they aren't), they just have to be toned down a bit. Look, as always, on Master of Magic. City positioning was very important, landscape influenced max city population, gold and production boni among other things, but these benefits were added to what the town population had done. Even a all-mountain town with coal and iron with +50% production, but small, was building slower than a thriving metropolis without any productivity perks. Balance is the key word; balance between what terrain and population does.
Keeping population a critical resource has another benefit: it directly influences your military output, or unit output overally. Settler spam is a big problem right now, but it can be countered easily. If a settler unit costs 20 citizens, and each one vastly contributes to food, tax, and production, training several units from the get-go is not only costly, it outright breaks your starting city. And if the monsters are more aggresive, you can't churn out settlers any more, it has to be a careful, well-thought out decision. This also applies to military units, if on a lesser scale. Every soldier is one citizen less, and going to an all-out war could cripple your economy. A quick idea: one faction could have more population growth than others, but weaker units and/or penalties to production, so the armies it will field will be vastly different than others', more hordish.
There are so many things you can do with population, please don't make it useless.