While many Taiwanese still see the United States as the ultimate guarantor of Taiwanese independence, they see China as increasingly capable of grabbing the island before the U.S. can intervene. So while the Taiwanese don't have to be strong enough to defeat a Chinese invasion, they do have to be strong enough to hold the Chinese back until American reinforcements can show up.
This is progress. And as Chinese power increases relative to our forward-deployed forces in the western Pacific, the amount of time that Taiwan needs to hold increases.
While this is welcome progress from their former attitude that Taiwan didn't need to worry at all about defending their island democracy since America would charge in early with guns blazing to save Taiwan, this does not solve the problem of keeping China at bay.
Yes, Taiwan needs to buy time and avoid defeat until American forces can arrive in the area. But what if Taiwan avoids defeat, yet fails to keep the PLA off of their homeland? The problem remaining is what if China gains a foothold on Taiwan? What if Taiwan is unable to eject those forces even after American forces arrive? A strategy of buying time usually means you must fall back and give up terrain as the price of that purchase.
Will we face a situation where, after several weeks, the US Navy arrives in force to contest the line of supply in the Taiwan Strait, American fighters slowly gain air superiority, and an American Marine regimental combat team and Stryker brigade start to flow into Taiwanese harbors and airports; but China has 100,000 combat troops dug in around one or more Taiwanese ports?
What do we do then? Do we spearhead the counter-attack with our ground forces, bombing Chinese forces with our precision air power? Do we counter-attack in force into the Taiwan Strait to cut off the Chinese expeditionary force on Taiwan and try to starve them into submission?
And will China risk the best of their PLA (they'd have to be the best to carry out a difficult amphibious/airborne invasion) and refrain from using nuclear weapons to retrieve a crumbling situation?
And will we agree to a ceasefire in place to avoid the threat of a wider, possibly nuclear, war between America and China? And then the Taiwanes and Chinese will both exercise control over portions of the same real estate.
Remember, avoiding defeat is certainly necessary to avoid disaster. But that is far from the only military mission Taiwan should aspire to carry out. It would be long-term disaster to allow China to get a foothold on Taiwan.
