Ah yes, because conducting the largest amphibious assault in human history on a mountainous island with dense forests would go so well... When the defenders have had almost a century to entrench their position and train literally their entire population in military service.

You start off with D-Day and jump straight into Vietnam. No military on this planet has enough conventional arms to take Taiwan by force.

If you really wanted to take over Taiwan, you could just naval blockade the island: it's substantially smaller than Cuba and has a larger population to feed.