The two statements are compatible. It can be true that there is a core of really high quality research coming out of China, and also that there is a huge “long tail” of low-quality research that is probably motivated by badly-calibrated publication quantity metrics. The US seems to be slightly more limited in this because (possibly) we have a smaller population of researchers, but also because our government funding sources for research (places like the NSF) tend to have some peer review that cuts against this sort of metric.