Great post.
I'd think you're correct. People emigrating are thinking about the future their kids will have in a place that will undoubtedly be communist dictatorship in 20 years. If it isn't already. I admire the people leaving. It can't be easy. Historically Hongkongers have always been brave to pack up to find a better life somewhere else.
You guys better cross Australia off your list of suitable migration destinations. We have redbacks hiding under the toilet seats here.
https://www.bbc.com/news/world-australia-37481251
It really depends on what is important for the person.
For me, I love the convenience in Hong Kong and I live in one of the busiest districts in the city. However, there are many people who live in NT, DB, Lantau who probably don't think the convenience is worth the negatives.
Same as the people moving to UK, US, vs HK. There are many things in HK better than US or UK. But personally, I feel the lifestyle in Hong Kong is getting worse. Sooner or later, that will converge to the point where the calculation of pros and cons start making sense to leave for somewhere else. For others, that point has already been reached due to their considerations e.g. kids, jobs, beliefs etc.
Some people also mentioned racism in other countries. I grew up in the UK and experienced it myself. It is not every day (or even every year especially when younger) but its still there and can be quite nasty. I'm a youngish male and relatively well built, so it did not bother me much. But I can understand others who may feel more concern for their safety.