Bibor
Doomsday Machine
Not true and a common misunderstanding.
Science only was forced to invent practical applications for their already existant theories. Only a hand full of projects were forced with massive investment of money and ressources.
The actual advancement in the war mongering countries were set back heavily during the war.
Peace is the time when science prospers. During peace you got a much higher overall investment in science and thus more overall advancement, not just a few technologies with practical applications.
When you research iron working you can plop out the best swordsman unit the era gives. That doesn't sound like a theory to me.
One might argue if we are still using jet propulsion airplanes (Me-262) developed in 1943 or are we using super-advanced jet propulsion airplanes. For me personally, the newest Airbus is just a copy of a copy of a copy of Me-262 until something truly revolutional replaces it (like an anti-gravity ship or something similarily impossible as a jet airplane was back in 1943).
You spend your peace earned money in buying these units and barracks you now need -> your country goes bankrupt.
You did not save some money? Well, poor you. What did you do with it, when there was no war? <,<
On relations with city-states, buying tiles etc.?
You tried to analyze the fabrics of the game so hard, yet you fail to see, that there is still the glue we had all along back from Civ I to today: your empire, your cities and citizen. They are still there and awaiting your orders to shift along your command. Just because Civ IV created another layer of "glue" which not one of the titles in the series resembles this strong, and this was taken away now, does it mean the "glue" was taken away? No it was only made thinner to be more fragile and unforgiving, more vulnerable to your strategy.
In Alpha Centauri you can do a lot of stuff, or buy everything with energy.
In Railroad Tycoon you can do a lot of stuff, or buy everything with money.
In Pirates! you can acquire all resources, or rushbuy them with money.
In Heroes of Might and Magic you can do a lot of stuff, or rushbuy with gold.
In Colonization you do a lot of stuff or buy everything with money.
In CIV4 you can produce a lot of things, or simply buy everything with money.
In all MMOs you farm everything by yourself OR almost everything with money.
...
Or to use CIV4 thinking again: you teched paper, traded around maps, got 1000 gold. Spent that gold on running the slider at 100% science. Developed a new tech, traded it around, got 3 techs and 1000 gold. Then you spent that money to rushbuy a very important wonder.
Original investment: Paper.
Returns: 4 techs and a wonder.