The reason people with means leave isn't because of impending collapse, it's because life is better overseas, today.
Or because they got their money in shady ways, and aren't interested in dealing with the consequences of getting caught.
They have too many old people and not enough young people.
It’s potentially possible that automation can solve this problem but China’s economy has relied on relatively cheap labour for growth and the shift from will be rather alarmingly sudden.
1. China has demographic imbalances
2. ???
3. "It is sad that so many lives will be lost in the famine that results."
That being said, they can avoid a production collapse by increasing productivity. China is building all kind of infrastructure like crazy. They need to move to first-world status, however, in the next 10 years or so. It’s going to be interesting to watch.
They are leaving because they want the luxuries of the West: Suburban lifestyle with cars, freedom to travel, freedom to invest globally, access to the best universities, access to technology like Facebook, Google and latest gadgets.
The one you're leaving out is rule of law and not having to living in fear of you or your business being seized by the government when the party feels like it (eg. crackdowns on the tech/tutoring industry, covid lockdowns). That's arguably the "instability" that you're talking about.