I mean it is
CHINA -- not Taiwan -- who cannot attack those landing sites.
The HK exercise was intended to have a 'force-on-force' battle
IN THE EVENT OF AN AMPHIBIOUS LANDING. The exercise is a
COMPONENT of a larger whole. Just in case you do not know the meaning of the word 'component', here it is...
https://www.merriam-webster.com/dictionary/component
Other related words to describe the HK exercise are: element, factor, or contribution.
Same idea with meeting PLA forces, on sea and in air, in the strait. Taiwanese forces do not have to meet Chinese forces head-on. Oblique attacks can be enough to slow advancement or even destroy critical parts of the invasion.
Get it?
This is why I said Operation Overlord is better than Desert Storm as applicable to a Taiwan invasion.
The problem with debating issues like this with no experience people like you is that you tends to grasp onto a single item as if that is the end-all. If a tank have the bigger gun, it will will. If a jet have faster engine, it will win. If a ship can run merely 1 kt faster, it will win. And so on...And on...And on...
Sheeesshhh...