You comparing apple and oranges. For one, KMT ruled China at the most instable/troublesome period of China's history from Sun Yat sen to Chiang. One thing is for sure, they both loved China and wanted a strong unified China. However, it wasn't easy to come by giving that troublesome period and the various warlords/foreign power preying on The Chinese(Soviet Russia in the north, Imperial Japan from the East , Great Britain/France, U.S from the South etc etc). So NO MATTER THE PARTY WHO RULED THAT PERIOD, it wouldn't have been easy for any of them to really build up the country and industrialised the country the way they wanted giving the state of the region/country back then and a world war that was being fought at the same time with a far more formidable enemy, while fighting rebels/warlords/militias at home. Do you think if it was the CCP it would have faired better AT THE PERIOD OF TIME? You have to know that its only when a country is united that they can even stand a chance to stand up and fight properly. The KMT couldn't since China was not really united back then. If the KMT had ruled a united stable China then i would have understood if you judged their track record. However they had so many things to contend with. The nationalists did try to modernise the Chinese Army for example prior to WWII, but Japan invasion and the fight against Communist rebels/warlords back then hampered all that eventually.
Moreover, KMT not being able to handle DPP is wrong. The KMT was drove from Chinese mainland by the communists, and when they settled in Taiwan they were still a one party state and ruthless to the inhabitants as well. However, with the passage of time, they realised that they couldn't keep up with this dictatorship, and they were ruling a far smaller country and so they didn't have any leverage whatsoever over any country/power. So they were more prone to pressure coming not only from fear of invasion by the communists in the mainland but even more so from the US(their only real support against an invasion). So their situation was totally different.
Imagine the CCP lost the war and fled to Taiwan, while the KMT adopted a more expansionist policy(they were quite nationalistic and they wanted to take back all the territories the GOD father of communism Soviet Russia illegally seized from China those past decades, i.e( Mongolia, part of outer Manchuria, part of central Asian states etc ). So in this situation Russia would have obviously viewed them as a threat and given their full support to the CCP to weaken them and create more troubles(like they did earlier in the 20s-40s). Do you think the CCP wouldn't have taken all the help they could from their only big supporter against an invasion by the KMT(and so would have obviously make concessions to the Soviets)? So i don't see why you judge the KMT differently. different situation demands different actions.
Governing/ruling a big country is different from ruling a small one.