I've spent a good amount of my research career working on (and sometimes in) China, with and without Chinese collaborators, depending on the project, and I have reviewed a lot of research by Chinese scientists.
It is excellent and remarkable how fast they are improving. In the late 1990s and early 2000s, Western scientists (mostly American and French scientists) were brought in quite a bit to help modernize the system, and it has helped substantially. The institutional resources and raw brain power available have meant rapid progress, especially once the Chinese grad students and faculty got up to date on the bleeding edge of research.
However, as with economic development, there are some substantial structural changes that need to happen in the transition from 'catch-up' growth to leadership. The biggest is a mind-set thing: There is far more respect for authority and confirmation bias in Chinese research than Western (especially American) research. In so many papers, the researchers go out and get great data and do a bang-up job of analyzing it, and then conclude by saying the results support the old hypotheses of the senior faculty who lead the research institute or some old Western luminary, regardless of the outcome of the analyses. I'm not going to say here that science advances funeral by funeral, but I definitely think that undergrad/grad students who grow up scientifically hearing about the cutting edge theories are more capable than older scientists of integrating the new theory them into their view of the world and their mental database of observations. This is required to further refine, develop or reject the theories and advance the state of knowledge. When junior scientists are not encouraged to rock the boat, then science advances much more slowly. Hopefully as national and institutional self-confidence increases, then revisionism (i.e. telling your boss that he's wrong, or that Dr. Famous American is full of shit) will get stronger.
The second is that, at least in my field, it is becoming very hard for Westerners to collaborate with Chinese scientists, and particularly to do fieldwork in China. (Note that I am a geoscientist and have mostly worked in Xizang province in Tibet, which has its own sensitivity issues). But I think that the government is deciding that the Chinese are caught up and then disallowing access to limit international competition. I can definitely see how they could feel exploited in a 'scientific imperialism' sort of way, and this is not at all restricted to China. But while this may lead to a more satisfying distribution of scientific fame for the Chinese, it also limits the rate at which the science advances. And Tibet is one of the richest areas in the world for studying tectonics and earthquakes, because it is vast, very active, and has essentially no vegetation so the quality and quantity of data is very high. Limiting access definitely means slowing down the rate at which we learn to understand earthquakes and earthquake hazards, and while there is a global downside (much of this knowledge applies to earthquakes everywhere), the downside is the highest for the Chinese citizens living near the faults that are not receiving as much study due to fewer researchers.