The British government has offered a pathway to UK citizenship to around 3 million residents of Hong Kong, who have British National (Overseas) status. I am not sure how many of the residents are going to apply, but this is a big blow for China. If UK goes ahead with its plan, then it will trigger a massive brain drain and eventually it will destroy the HK economy.
Hongkong is a special economic zone, I do not think it will affect their economy, the selling point of Hongkong is its real estate and people from around the world are flocking there to buy one and I do not think that the brain drain will destroy the economy because besides having expensive real estate to fund the economy, it is also a tourist destination.
Obviously which democratic country would want itself to be ruled by a communist again? No matter how ruined your country is people of this century still prefer democracy.
I wouldn't want to live in a communist country too, with stories from yesteryear about the hardships of the people living in communist states and atrocities committed by the people in those countries, it will be a definite pass for me. Democratic is the closest thing we have to a utopic government, if only the masses are actively participating in the community and they care about the social injustices happening then democracy will work as intended. But we can't have that because of human's primal instinct to compete with one another.