The reality is the Taiwan isn't broadly recognized as a sovereign country, so it doesn't wield the same authority as an independent nation in terms of international agreements, trade, etc. It doesn't have allies who would defend potential sovereignty, and it doesn't have enough guns or money to leverage itself as independent. That's way more important than some abstract discontent some people feel. At best you could say Taiwan is a Chinese client state.

Countries don't exist because some people feel like they should be one. I could ask you to talk to a Texan secessionist and tell them their cause is hopeless.

I will tell a person living in Taiwan they live in a province of China, sure. I don't care. Their government is the remnant of the defeated nationalist faction and I have no sympathy for it. I have way more sympathy for the Gaoshan and other indigenous Taiwanese people who aren't represented well. Taiwan will hopefully get reabsorbed into the mainland within my lifetime.