Exactly. China is never going to agree to an independent Hong Kong. Ever. It’s a ridiculous demand. If Hong Kongers are struggling against police armed with “non-lethal” weaponry, what’s going to happen when they try to declare independence and tanks and the world’s largest standing army come pouring in the border from Shenzhen?
The protestors should focus on pressuring China for a full-democratic vote while remaining within China as “One Country, Two Systems”. They do have some leverage. Hong Kong is still an important part of the global financial system and is a good bolt hole for the more corrupt Chinese elites to get their money out of the country (which includes probably all of the PRC leadership).