It's moreso the emphasis on quality control.

You can have whatever manufacturing requirements you want, but if a substandard product (because, as an engineer, you'll know that it's impossible for 100% of products manufactured to be perfect, no matter your Quality Assurance processes, purely down to random chance eventually) makes it past QC without actually being properly checked, that product which is defective in some way will make it to a consumer.

Sure, it's impossible for every defective product to be found, but a robust enough QA/QC system should be able to catch the vast majority.

Unfortunately if your QA/QC standards aren't high enough, and you say 'Good Enough', then a shoddy product will make it through.

Different parts of the world have different cultural acceptance of 'Good Enough'. Which means if the foundry that makes the steel buys in poor quality coke because 'Good Enough', then chances are their steelmaking process is 'Good Enough'. Then whatever raw feedstock they produce might not be great quality, but hey, 'Good Enough'. If the market accepts it, why bother making higher quality steel when you won't make more money and you'd end up spending more and reduce profits.

The casting foundry receives this poor quality steel, goes 'Good Enough', melts it down and casts it, but they don't cool it properly to ensure the right properties and phase structure. But hey, 'Good Enough'. The shoddy castings get a quick once-over, stuck in a box, get a QC stamp, and get sent to the factory that fits them to a final product.

The final factory sees the shoddy castings, but hey, 'Good Enough'. If they reject them then they'll have to slow production, and the foundry might stop supplying to them. They'd have to get more expensive castings from a different foundry. But if the consumers will tolerate it, hey, send it through, fit it, and your shoddy product gets made 'Good Enough'.

You can specify whatever manufacturing processes and requirements you want, unless you actually stick to them they're next to worthless. And if your entire factory doesn't give a shit enough about sticking to the process, guess what? They'll make shitty products.

China can definitely make high quality products. Anker is a Chinese brand of powerbanks and charging products, and they're pretty damn good. Only because they place a legitimate emphasis on high quality processes.

Unfortunately, it's cheaper to make shitty products, so as long as the market will accept shitty quality, the factories will continue to produce shitty products.