I was trying to illustrate the broad chasm between theoretical and practical expertise. Just because someone "knows a lot of STEM" doesn't mean they can actually produce a useful thing. China already had perhaps the most highly concentrated amount of manufacturing engineering expertise anywhere in the world, yet still they needed help with what most people would consider a basic item.

This is fine! Most countries, as you noted, are in the same position. It's a desirable outcome of globalization.

It becomes problematic, though, when your goal is to build an incredibly complex machine that requires expertise beyond your own (like a particle accelerator, perhaps) and the people and countries whose help you require are unwilling to work with you.