It is not the critisism, that I can take, it is the staring yourself blind on the wrong thing.
It is not a problem as it is now with the Prehistory, and only slightly with the Ancient Eras because these eras Civics have inflated maintenance costs, they have been "patched over". That is why you have trouble expanding during these eras. I will try to show it differently:
Prehistory:
City Maintenance
Low Base and
HIGH Civic inflated +
LOW income to battle the costs=
hard to expand, high costs for the few cities one can set out.
Reaching the NumCity cap is nearly impossible, no problem occurs.
Ancient:
City Maintenance
Low Base and Middling Civic inflated +
Middling income to battle the costs=
Slightly easier to expand but still reaching a cap that is hard to overcome.
It is possible to reach the NumCity cap but still har dot go much past it as income does not make up for new cities placed with middling income.
Classical
City Maintenance
Low Base and
Low Civic inflated +
HIGH income to battle the costs=
Fast and furious expansion can commence.
Passing the NumCity cap is easy and once that is done there is no stopping as
High and rising incomes facilitates more and more expansion.
Later eras do not reduce Civic costs to city maintenances more, the base stays the same, but Civic Upkeep and Inflation starts to matter in an effort to reduce the ever increasing income.
The amount of cities a nation can have is only limited by the space available as each city, with ease, can pay for both itself and the costs of units once being a middling city. Possibly only budding cities do not yet pay fully for themselves but with a few

buildings they start doign so pretty fast.
My test is to swhow this. I keep my expansion and income low,
not by choice but because that is how the game is designed, until I pass Writing and start reaching all those late Ancient/Early Classic Civis. Then I could hyperexpand, with ease.
To even attempt to fix this without setting "city limits" or inflating Civics even more (which only helps make the problem worse) the Base city maintenance costs need to be adjusted. Those have not been touched since C2C started, probably not since AND and ROM started either but in AND and ROM there is not as much in incomes, mapsizes, resources, that skewer the "maintenaces v income" ratio up as badly as in C2C.
In the Core game I still beleive the NumCity handicap numbers should be at least tripled. This sounds like a drastic change but consider taht they probably should have been slowly raised throughout all the 34 versions that have been and you can see that it is not a lot if it had been done little by little (Diety from 8 to 24, 16 steps, less than +0.5 per version, Noble from 5 to 15, +1 every 3 version, and each version brings more income and more stuff), as it probably should have been.
For SO's Nightmare mode that can be increased more. Maybe not to the numbers I am testing at (Diety 70, Noble 35) but still higher than what is set in Core.
On top of this, as the NumCity numbers are not the only ones needing adjustment, the WorldInfo NumCities- and Distance-Maintenance also need adjusting. Again not as drastically as I have set, and what numbers are good probably need a bunch of playtesting to find. Suffice to say they need 34 versions of changing too though so the increase might look astronomical at first, though no where near my x35 (Duel) through x65 (Gigantic) increases. x10 to x15 might be a good starting point.
The DistanceMaintenance in Worldinfo needs flipping around too, smaller map should have higher distance cost, larger should have lower, somehow these have been reversed.
The current numbers are way off though and these two things, NumCity in Handicap and # and Dist in WorldInfo, have together ensure that "patching" via City Limits and inflated city maintenances in Civics has been introduced and set over time and 34 versions. Patching over a problem will not help in the long run though, only make it worse and worse.
The "patching" that has been done to limit the early expansions in Civics also needs reverting. Keeping it will only keep the huge difference once the "right" civics are taken in any game again.
So those highly inflated NumCities and Distance for a lot of the early civics do need removing or you will end up with the reported -50

/turn problem instead.
Anarchism also has a special problem, the early Prehistory actually, as incomes are at 1/3rd normal, maintenances for cities, at least the 2 first, should be almost completely removed. Let units govern the capital completely until Tribalism, makes more sense anyway I think.
Cheers