The 1 country 2 system did work pretty well for CCP!
They have openly breached an international treaty and taken over HK, with no actual cost to them, except for a few bad words...
So why not repeat it in Taiwan?
A) "1 Country, 2 Systems" should only apply to two regions of the same national sovereignty. Thus, it doesn't apply to ROC vs PRC.
B) The reason for the Civil War in the US was precisely because "1 Country, 2 Systems (i.e. slavery states vs slavery-free states)" would not work.