The way I see it is this: If you can build it now, it's not the wonder of the First Age people are thinking of. If you can build a factory-cathedral now, then the factory-cathedral you can build is not what people during the First Age would have called a factory-cathedral.
The reason for this is infrastructure.
If there were a terrible cataclysm tomorrow and a thousand years later, the world were just pulling itself back up to a Renaissance level of technology except for a few scattered bastions of learning, those few scattered bastions of learning wouldn't be able to build a modern car factory, and nor would it be useful to them if they could. In order to build a modern car factory, you don't just need people who know how to build it. You also need separate factories to build assembly-line robots, and those factories need factories to build computer chips to power the robot-part-assembly machines. The whole thing is an interlaced web of infrastructure that spans continents. Furthermore, in order to be useful, a car factory needs a world crisscrossed with roads so the cars can have places to go. Those roads need more infrastructure to build and maintain.
The First Age had all that sort of thing. The Second Age does not. It doesn't matter how Awesome you are; you can't build the factory-cathedral, because the people in the First Age were applying their Awesome to build the infrastructure that made the factory-cathedral possible, and the Awesome doesn't make the factory-cathedral need less infrastructure — it makes the factory-cathedral need Awesome infrastructure, which is in fact harder to build. You are not less screwed by being Awesome, you are more screwed.
Now, some Exalted players will respond to this with "That's not fair! You're making my character less Awesome by saying there's stuff he can't do!" To those people I say suck it. Sometimes for the setting to make sense, there needs to stuff you can't do right away. If you want to reach the First Age's heights of Awesome, you will need to rebuild the world-spanning infrastructure that made it possible. This may take centuries — good thing Solars live that long.
Not all sourcebooks agree with me. Some sourcebooks suggest that rebuilding the First Age's heights of Awesome is as easy as making some rolls that Solars can easily make in a couple of seasons. Some sourcebooks suggest that there is no way you will ever have enough time to rebuild the world-spanning infrastructure, because there are too many threats and they're all allayed against you at once and you need to deal with all of them and so the world is going to end in five years, sorry. I maintain the sourcebooks that disagree are stupid and wrong and not in keeping with the main thrust of the game's premises and should be ignored or modified.
You're talking the difference between the Ford Model T and an aircraft carrier with a full compliment of Predator drones. For these purposes, infrastructure that still exists but in a reduced capacity does not exist at all.
Remember, Lookshy was only able to build a crappy, reduced-function version of a Kireeki-class skyreme, and the Kireeki-class skyreme is basically the steam-powered paddle wheeled riverboat of military skyships. Being able to scrape together the resources to build a paddle wheel doesn't mean you can make a nuclear sub.