But landing troops (they can't march, it's an island, and the difference between amphibious and land based operations matters a lot) would be extremely difficult, and not obviously in the PLA's favor. See, for example:
https://foreignpolicy.com/2018/09/25/taiwan-can-win-a-war-wi...
Besides that significant causalities and economic damage to both sides, which of course they'd eventually win, but it'd be a geopolitical disaster that won't end with the quelling of the armed forces.
China has far more to gain not going this route.
Although it would assuredly take some time to ramp up, TSMC should be able to spawn fabs outside of Taiwan, out of CCP reach. They are already building one in the US, albeit with a small output.