Most of those jobs outside of a few narrow categories were lost to automation. We make more steel, aircrafts, and cars than ever but with far fewer people.
China's history of planning has led to tons of misallocation of resources, and I'm not sure I'd want to emulate that.
Of course automation plays a part, but it is nothing like the whole story. China now has far greater capabilities to make critical components from chips to solar panels than is located here. Look what happens to our supply chain when supply is just reduced a bit. What do you think would happen to our economy in a conflict?
>>China's history of planning has led to tons of misallocation of resources, and I'm not sure I'd want to emulate that.
Of course we wouldn't want to emulate that; that's a strawman argument.
But to use that argument to avoid planning altogether is foolish. And yes, resources will APPEAR to be wasted. Keeping more than minimal capabilities immediately at hand is "inefficient".
This is the same as exercising and eating right to stay in good physical condition - no one needs to be able to lift weight and run fast for 99.99% of modern jobs. Yet it is a good idea for many reasons. By your argument, why bother to save for emergencies or tough times? That's inefficient - you should enjoy your full income right now - heck, go into debt too!. Also by your argument, we shouldn't plan to avoid technical debt - that's inefficient waste of programmer time - just write the first thing that comes to mind to deploy the feature.
"No plan survives the first shot of the battle".
So, sure, the plans will likely not survive in any detail even a decade from now.
But the fact that they are making plans, attempting to understand the considerations of those future generations, understand what strategic goals need to be worked on now to help that, and more — this is critical.
I contrast, western politics and decision making tends to focus on considerations that are at best hot for the next election cycle.
And notice that the US is not now trying to return manufacturing home because of long-term plans, but because the people noticed that the bargain of cheap goods from China doesn't mean much when you exported the job. The fact that China now makes and has access to key components in some key military systems and that needs to be reversed barely enters the mind of the electorate.