Taiwan is not a signatory to the Treaty of San Fransisco, 1951 (Text: https://treaties.un.org/doc/Publication/UNTS/Volume%20136/volume-136-I-1832-English.pdf).
It's the weekend, you can go read it. It is this treaty Japan use for it's application to the United Nations.
Here is how the China delegation was reassigned from Taipei (Taiwan) to Beijing (Mainland) in 1971:
https://en.wikisource.org/wiki/United_Nations_General_Assembly_Resolution_2758
If you know, can you point to a Treaty or Resolution that establishes Taiwan as an independent country? To their declaration of independence? To the date of their founding, not just the date of their first election after the fall of Martial Law in 1989?
If you want Rule of Law and Treaties, you have to follow the rule of law. That means sometimes, people you don't like win.
If Alberta declares independence does that mean that Treaty 6, 7, 8 (which Alberta was not a Party to but Canada is) no longer apply? Can the United States protect Alberta as an independent sovereign state (not it's own territory) that aligns with its own interests?
If you believe in Treaties and Rule of Law then Taiwan is a Province of China and Alberta is a Province of Canada no matter the declarations of the politicians (Premier of Taiwan nor Daniel Smith) or other countries' interests.
What you want is to define everything you want as Rule of Law and everything you don't want as criminal or aggression. Then you convince people to follow "Rule of Law" which just means they can only agree with you and die for what you want but you don't have to follow anyone else.
I have listed primary sources, while you have just made statements with no backing.
You can choose to die and give all your money to RoC (Taiwan) instead of dedicating your life and resources for local causes. You are free to do so. It happened in the Spanish Civil War, a cause I and George Orwell agree with, because the government did not dedicate any resources to protect the Spanish Republic from Franco.
What I don't want you to do, is try to convince my family, friends, neighbourhood and country to shed blood and resources so you can play map maker to aid people who want to abrogate a Treaty. Because there will be a time (soon) when people (Daniel Smith, Pierre Polievre) will want to abrogate Treaties (Treaty 6, 7, 8, Rome Statute for the International Criminal Court) and when we ask them why they can they do that, they will point to you.