The UK only tried to introduce it after they knew they couldn’t hold on to Hong Kong anymore. So they did it out of spite.
But the UK did try to convince Portugal not to offer the people of Macau citizenship, because they didn’t want to do the same for the people of Hong Kong.
It appears Britain only tried to give them democracy when they knew the writing was on the wall. That seems disingenuous to suggest it was China that blocked them.
While technically true, if Britain truly wanted to help the Hong King people, they would have offered citizenship and let them immigrate, like Portugal did for Macau.
Instead, the British tried to stop Portugal from doing so, because they didn’t want to offer the people of Hong Kong citizenship.
But the UK did try to convince Portugal not to offer the people of Macau citizenship, because they didn’t want to do the same for the people of Hong Kong.