I think I largely agree with you, but I can't tell if HornWumpus is making his point badly or just trolling. I would say that the communists certainly could invade and conquer Taiwan if they wanted to, but there would be a real cost and they would have to evaluate the benefits, including the effects on "domestic politics" in their peculiarly anti-partisan one-party system.
They could even imagine making a profit out of the invasion, but that obviously depends on not destroying too much infrastructure and a belief that the majority of the people on Taiwan would accept the new situation. An expensive insurgency could absorb all of the potential profits for as long as it lasts. On that aspect, they are obviously much more capable than we are of assessing the popular sentiment of their fellow Chinese.
Having said that, they might be able to invade relatively inexpensively by merely filling the next batch of cargo ships with soldiers rather than cargo. If they land and successfully seize the ports in a surprise attack, then they could quickly ferry a few million soldiers over and have quite substantial beachheads. I'm not even sure if the relative air forces would matter if the communists pulled a surprise with clouds of cheap drones...
There is a really important time-related factor, too. There was a known date for Hong Kong and they just had to wait. Taiwan has no schedule and they do NOT want to wait forever. They may well see #PresidentTweety's apprenticeship as the golden opportunity they've been waiting for.