But we build in response to demand. Once people need more of something (e.g. PPE), production ramps up. That effect has been in place and has worked quite well for thousands of years. It doesn't require any policy or government, or even a new social movement, it's just an emergent property of humans being free.
You might argue that we could be smarter, and that we should build excess PPE before the demand hits just in case. This is reasonable to an extent, but probably to less of an extent than you think. The problem is that there are dozens of possible scenarios we should prepare for, and we can't know ahead of time which one is going to strike next. We have to prepare for them all: nuclear bunkers, asteroid deflection, global warming mitigation, sea walls, military capacity, etc, etc. Giving the competition among possible future disasters, it is often wiser to KEEP YOUR POWDER DRY (in capitals, because that is my main point) so you can respond to any of them after they eventuate, not before. This requires that we have the capacity to ramp up production quickly. That's not always a given, so I'm in favor of governmental action to ensure we have "stragetic capacity" to ramp up anything we might desperately need. But I'm not in favor of just building lots of things that we might need.