It's 2019, not 1949. Taiwan is anti-CCP because the PRC claims its territory and Taiwan overwhelmingly rejects the notion of being ruled by them. Which is fairly natural, I can't think of many people in developed, democratic countries who want to be ruled by a neighbouring, developing dictatorship.
Taiwan is thus still formally a province of China in the general sense of 'China' and is claimed by the PRC because of the civil war and because the PRC claimed to have superseded the ROC (which obviously the ROC/Taiwan does not agree with)
This is unfinished business since 1949.