This is not how naval building strategy works. Precisely because "light forces"(mobilization ones) are (1)fastest to build, (2)expensive to maintain(relatively and absolutely), (3)manpower intensive, (4)have insufficient peacetime use, (5)decay quickly in their capability(mechanical obsolescence), (6)suffer the most from theoretical as opposed to practical wartime experience.
Building the wrong craft at the wrong time won't buy you more preparedness. It'll only turn a lot of precious resources away from what actually matters - and those who'll start actual buildup later will get a better force.
Many countries tried this "fast" route and suffered for it pretty hard, wasting a lot of resources (and continuous expenses) for little gain.
PLA doing naval buildup the way they're doing it only says that the quality of governance in China is actually high. People making decisions either know naval theory themselves or, at least, listen to those who do - and continue to do so for several terms of various heads of the state. This is actually impressive, and god bless those who are still blind to see it.
You seem to be neglecting one possibility: continuous replacement. You aren't contesting @Hendrik_2000's statement that the LST/LSM landing boats are cheap. So why not continue to build them? Just retire the oldest boats and replace them with fresh new ones, and keep doing it, for decades if necessary. Why not, they're cheap!
I also agree with @plawolf's suggestion of bringing prefabricated docks. Perhaps the PLA can do both: use landing boats to take and hold beachheads, then install prefabricated docks. Then fewer LST/LSMs would be needed.