It's outdated that Carrie refers to Hong Kong as "the gateway into China", this may have been true in the 1980s but now the mainland is well connected to the rest of the world with either direct flights or one stop connections via multiple hubs both within and outside the country.
3 weeks quarantine is an absolute killer for any visitor interested in coming, it's far longer than most people would stay in the first place. Cities such as Hong Kong, Singapore and Dubai aren't places where people stay very long anyway. They rely on huge numbers of people turning over quickly.
Thailand's strategy of a test on arrival and one night in an approved hotel until the result comes through would be acceptable for the vast majority of people coming in, even those only staying for the weekend.
Sinovac has similar protection to other vaccines in preventing serious illness but is way behind in stopping people from getting infected.
A zero COVID strategy with a less effective vaccine isn't going to work while other countries have more effective vaccines and are preparing to live with the virus while they open upon.