You have to imagine how the world is like at very large scale. There won't be enough food to go around. And it takes very little chaos for systems to come down. World would go into full chaos mode when some of these problems come up that will be declared unsolvable. Hundreds of millions of people may be billions of people would be deemed unsavable. World is held together by soft illusions of safety and sense of continuity etc. When it starts to fall it'll be full irreversible chaos.

The high capacity and advancements of the modern world aren't accessible in an unstable world. Its not even redoable even if all the knowledge is safely stored away. It would be impossible to recreate that momentum that made the modern world possible.