I m not overestimating or underestimating anyone.
Neither China is Russia nor Taiwan is Ukraine.
Let's go with the simplest way,
China goes with the Scorched Earth policy. We are seeing this in Gaza.
At its closets, the distance between China and Taiwan is around 250 Km, WS 2 has a range of 350 KM according to some sources. Now normally it won't be just ballistic missiles. it will be massive swarms with hi-low weapons.
even with ballistic missiles, the time is minutes not hours. even with all systems fully ready to intercept, it will not be able to hit everything even 10 to 20 % of ballistic missiles hit its target what do you think will happen I'm giving an 80 / 90 % success rate to all Taiwanese systems combined working perfectly.
Taiwan is not a large Country even with saturated systems, no one can give a 100% success rate.
China can set a no-go area close to Taiwan 100 - 200 KM away , and blockade at a relatively safe distance.
The biggest advantage and its weakness is its location. it's an island nation that can be blocked. Very limited in its space, in large countries if you have a large enemy pushing. you can retreat and re-group and attack again. but in the case of Taiwan where you retreat.
Check the average age for Taiwan. it's not young people. War is not just about shooting missiles. With the destruction of the Taiwanese system, China can just literally sit back and hold its troops back and lower its losses. Both can fight with AD systems and can hold off large military pushes but Taiwan can't survive for long when it has no supply routes open.
How will they provide to the people? How you will provide for the military.Even if Taiwan controls around 150 KM of its zone. China can just out reach Taiwan.
It's all nice and Good but in the modern world, no one wants its people to die for some other country.