Its not that Taiwan was unwilling to upgrade its forces, its just been unable to obtain modern weapons. Nobody will sell them any, or components to make its own advanced aircraft.
Taiwan has been an industrial nation for many years, long enough they should have tooled up to build indigenous weapons or even knock-offs. Too many nations threatened by communism have neglected their self defense, expecting Uncle Sam would come to their rescue. Now that we are 20 trillion in debt, we can’t be depended on.