So, no, it doesn't make any sense in the current age to say you own guns to protect yourself from the government.
Except that an army cannot fight on 10 fronts at the same time. When you have a whole country turning against you, you can't be there at every single place every second with a regular army. On the contrary a regular army would be beaten up in no time.
You also have to take in account that it's much more likely there would be rogue generals turnings against the power in place so general + armed people is a good catalyst.
The CIA also has a document (sorry, I don't remember the name) detailing ways that civilians can sabotage efforts by doing things like holding extra meetings, etc.
I wonder if anyone would stay in the military to better thwart it.
https://www.cia.gov/news-information/featured-story-archive/...
That's probably not the case for HK.