The Taiwanese have rejected the Chinese notion of one country and two systems (that is, Taiwan could continue to run its own affairs if it submits to Chinese authority) by highlighting their embrace of democracy despite China's demand for unification:
On Tuesday, President Tsai Ing-wen of Taiwan gave a New Year’s speech in which she said her 24 million people insist on freedom and democracy, unlike on the mainland. “China has to face the fact that the Republic of China [Taiwan] exists,” she said. It should use “peaceful and equal terms” to deal with differences.
The next day, in a speech solely about Taiwan, President Xi Jinping said in Beijing that “differences in [governing] systems” should not be an excuse against unification, an idea he called “inevitable” and perhaps made possible someday by force. The people of Taiwan are part of the same “family,” Mr. Xi insisted, which he called the “Chinese nation.”
Well, the Taiwanese have eyes. Democracy is "further out of reach" in Hong Kong. Did you expect anything else from China?
And ears. So duh.
This author thinks that Taiwan could not defeat an invasion and must work to increase China's perception of the cost of invading, including combat losses, economic losses, and international isolation.
Although I don't think a traditional beach invasion is how China would invade, China can invade.
Worse for Taiwan, all China has to do to doom Taiwan is seize a bridgehead and survive to a ceasefire.
It is true that China has a level of casualties to take Taiwan that they won't pay. But that price China is willing to pay could rise dramatically depending on internal Chinese circumstances--like legitimacy shattering economic problems.
Remember that party supremacy is more important than anything else as far as the Chinese Communist Party is concerned. As the post about economic problems indicates, China spends more protecting the party from internal threats (the internal security budget) than it does protecting China (and the party) from external threats (the defense budget).
And even if some internal event doesn't prompt an invasion regardless of the cost, the growing military imbalance in favor of China will get to the point where Taiwan's only path to survive as a democratic and free country is to own survivable nuclear weapons or somehow convince ordinary Chinese that their military shouldn't conquer Taiwan--or even inspire a revolution in China.