Submarines, as instruments of guerre de course, are an asymmetric counter. They're specifically bought to remain relevant even when a direct counter is impossible/counterproductive(wasted resources).
Larger numbers of ASW forces won't deny submarine force its ability to produce impact. Because in the end, it's up to the submarine commander(and command) to decide where to engage, how to engage, and wherever to engage at all.
Until and unless ASW force can proactively hunt down submarines(and this isn't something current PLAN and PLANAF is aimed at, at least not "behind the corner" of Taiwan island itself) - they're going to matter anyway. In some cases, they can matter even after a conclusive military defeat(ww2 cases).
The discussion isn't about whether submarines are better than "nothing" or whether they're better than a "direct counter" (I assume you mean surface naval forces for example).
The discussion was about whether the ROCN's procurement of 8 submarines of their specified size/displacement is the best procurement choice considering other plausible alternatives -- e.g.: if they went for 16-24 smaller SSKs of under 1000 tons instead.
The discussion was also about whether procuring submarines in general was a wise use of opportunity cost in general as a strategy against the PLA specifically and the expected political resolve and military capabilities the PLA will be seeking to bring to the table, and whether alternative procurement/doctrines might be a wiser and more cost effective choice than submarines.
This impressive list won't keep MG nest on an unknown hill(bamboo grove, slit in a cliff, you name it) suppressed. Even drones in Karabakh were doing an impressive, but different job.
I.e. until and unless there are beachheads of sufficient depth, and even assuming all these fires can be freely used at Taiwan w/o reserve - with all those capabilities, the attacker is still going to be at a massive disadvantage.
This isn't about China specifically, other than China and US, no other country is capable of doing this anyway.
This is about strategic landings against prepared position being difficult, no matter whom we're talking about.
I agree in principle that of course amphibious landings and developing beach heads as a matter of principle is difficult, "in general".
The stages of an operation are basically all the same:
1. Softening up of a beach head and its immediate vicinity through use of fires
2. Landing of forces to seize and clear the immediate beach, setting up a perimeter
3. Preventing reinforcements from other areas to come and reinforce the beach/prevention of counter attack (aka isolation of the beach)
4. Simultaneously with the above, establishment of a beach head to land heavier forces and logistics to allow you to move in deeper
There are also other stages not mentioned but which are implied:
0. Massive bombardment and destruction of the air force, navy, command/control, air defenses, artillery systems, logistics, sensors etc
3.5. Locating and destroying any remaining artillery or fires systems that are still able to present a threat to your landed forces from indirect fire.
But the seizing of a beach head and reinforcement of a beach head is dependent on a case by case basis, the question is whether we think the array of air, naval, missile, and amphibious forces on the respective sides are capable of enabling or preventing the above from happening in this specific case and scenario.