Naval landings are never easy. Suicidal if you don't have complete air dominance. In World War 2 the Nazis were able to conquer all of western Europe in weeks

Naval landings are never easy. Suicidal if you don't have complete air dominance. In World War 2 the Nazis were able to conquer all of western Europe in weeks, but were completely stopped by the mere 50 miles of English Channel. And this was in the days before Radar was well understood and deployed and before guided cruise missiles were a thing. There is only one scenario where the invasion of Taiwan isn't a long and drawn out affair that costs the Chinese hundreds of thousands to millions of troops, and that's the one where they start off by nuking it flat in a massive surprise attack and end up winning only a radioactive wasteland for their troubles.