Earlier quoted context omitted.
> it would be a pity if nobody came to the rescue when China eventually puts its Taiwan plans in motion! Wouldn't that just mean that Taiwan has to choose between two villains, and China can take the advantage of this by changing its narrative and taking the position as a hero, protecting Taiwan from the US.
Taiwan really, really does not want to be part of China. Or rather, they see themselves as the legitimate government of China, which is undergoing a temporary Communist junta. The separation was extremely violent. I mean, you saw the Three Body Problem. The US fosters this, to retain a toehold there. Taiwan doesn't exactly love us for it, but they know which side their bread is buttered on.
No, they don't. But formally renouncing that position[1] makes them officially secessionist in the eyes of Chinese conservatives, adding pressure to invade. The One China fiction matters, though how much it matters is definitely up for debate. But it's a local minima, and rolling the dice comes with significant risk.
[1] At the state level. AFAIU, it's been renounced by several of the major parties in Taiwan, and when in power they've made movements at low levels of government that arguably contravene the policy. But it still remains the official position and its still enshrined in the Taiwanese constitution. And, yes, the US adds pressure to maintain the status quo as it would (might?[2]) be on the hook for the defense of Taiwan. But the majority of the population isn't in favor of formally renouncing it, either; the potential negative consequences are existential, and the material benefit is slim to none.
[2] During Trump's first term it was claimed he privately admitted that if China invaded Taiwan he wouldn't intervene.