We had some pretty wide-ranging discussions about this back in Civ VI days, and I'll repeat what I said then:
The actual amount of Resource or raw material needed was for most of history small enough, or in small enough parcels, that it would be delivered if you needed it bad enough (ie: were willing to pay for it). A Roman Legionary could be completely equipped with iron-based armor, weapons and equipment using about 50 - 100 kg of iron ore or less than 50 kg of 'raw' wrought iron. That's 1 - 2 donkey packloads. An entire Legion of 4 - 5000 men could be equipped for about 200 - 250 tons of iron, or about 3 - 5 Classical shiploads.
So 'raw material shortages' as long as the material is available anywhere, was never a thing: Tin from Afghanistan or Cornwall made the Bronze that powered the empires of Mesopotamia and Myceneans in Greece. The Chinese famously traded silk, porcelain, and other 'high tech' goods for warhorses from Their Enemies, the Northern (steppe) Barbarians for centuries. As long as you didn't have to cross wide areas of Deep Ocean, there was always a way to get the resources.
That is, until the Industrial Era (beginning of the Modern Age, roughly, in Civ VII). A single kilometer of single track, relatively light railroad requires 100 tons of iron or steel rails. Add in iron for locomotives, car wheels, sidings, stations, water towers and other required auxiliary equipment and even the shortest railroad requires as much worked iron as the entire Roman Imperial Army did. Furthermore, even a small steam engine with compound cylinders (common after 1880 CE) requires more precise machining and manufacturing techniques than anything built before 1776 - before that approximate date, they couldn't even build the machinery to build the machines required to make s team-powered ships, railroad locomotives, or modern artillery 'work'.
By 'changing the rules' for each Age, Civ VII starts to approach the massive changes that took place in how and what could be built pre- and post-Industrialization. Unfortunately, they almost completely miss the political and social changes that Industrialization brought: as in, it created an entirely new class of people in industrialized societies: the Urban Factory Worker.
Cue Marx and Engels, the British Labor and LIberal political parties, German Social Democracy, the Labor Union movements in every nation. Only later, in the 20th century, did these and other effects spawn the Ideologies that the Modern Age in Civ VII focuses on. I think it would have made a much more interesting game if you started the Modern Age having to deal with Railroads, Factories, and a radical change in your political and social society, and then later also had to deal with Ideological Conflict: two 'Crisis Periods' in the Age, so to speak. giving the gamer escalating problems to deal with as he/she claws their way to 'Victory'.
