Exactly this is the case as Hong Kong in contrary to Taiwan was a legal subject in the eyes of Beijing, as @clearwaters said HK is a Special Administrative Region. On the other hand Taiwan is more some kind of a heretic region which never got official support for anything since it's in an eternal segregationist state from its mother land. I took rather the perspective from Beijing than the international perspective, although HK enjoyed quite lots of economical freedom and benefits as well compared to mainland China. For example just recently HK got hit by the US sanctions which actually hurt China the most since they profited from their loophole in the South.Yeah, I was just commenting on the point/wording of HK being 'Taiwanized', which I reckoned was not accurate as Taiwan even before the law may have been more free than HK (?; thinking about the developments in recent years; China meddling with HK elections? edit. the '31 August Decision' and the electoral process by committee), but certainly after. Taiwan has a democratically elected government (as you stated), own army etc. But their predicament as well has worsened over the years. More and more pressure in many ways. As per the article above: "In addition to hardening its rhetoric against Taiwan, China has sought to isolate the island diplomatically. In the last five years, Beijing has poached seven of Taipei’s formal allies, leaving only 15 countries that recognize Taiwan as an independent country."
Only 15 left that recognize Taiwan (and maintain official diplomatic relations). I recall the situation for long being that Taiwan is rather free to operate economically, but not so politically. E.g. they are part of the World Trade Organization, but not UN (as you noted). But still maintain political freedom within the country.
So they treated HK already as an ordinary Chinese city where the CCP can make their business. Or as a famous controversial politologist from China explained, HK will be the new Tibet. Whenever they will benefit from their unique situation, they will milk that out for cash. However, the state of a 'Special Admiministrative Region' with the One Country, Two Systems mantra is led ad absurdum since Beijing is more or less openly dictating what will go on in HK. Whereas the people who still fight and protest for the UK-China treaty and its 50 years of maintenance (aka democracy) will get bullied just like the Taiwanese state.
I don't see there any improvement from the former HK, which had quite a comfortable situation economically and politically as the situation was stable and many companies outsourced to there, to current Taiwan. It's actually a downgrade since Taiwan never could have these benefits tolerated even by China like HK did. Well, did, since it's in the process of becoming your typical Chinese metropole.