Anecdotal experience can often be misleading, that's why statistics are valuable. It's clear that at least some students are returning, and now thanks to rampant racism in US a lot of ethnic Chinese scientists are going back to China.

At the end of the day, a single individual can educate many thousands of people or produce high quality research that will advance the country. There's a pretty famous case of this Qian Xuesen who is the father of Chinese space program. He got his education in US, and then left to China during the red scare.

https://en.wikipedia.org/wiki/Qian_Xuesen

Many thousands of people like him are doing the same today.

And finally, researches are leaving Europe for China nowadays as well https://www.bloomberg.com/news/newsletters/2023-07-19/china-...

However, all that aside, the most important point is that China has a very good education system that's accessible to everyone, and they have a large population. This is coupled with government having a lot of direction over the industry and actively funding the types of research and technology development that's strategic for China. This is a recipe for success.