The issue is not building a navy. The issue lies in the force composition.
USA built a massive navy by the mid 1940's because of it's global interests that were constantly under threat in the previous 150 years. From U-boat campaigns, to tiffs with Barbary Pirates, to forced Impressment by the British, to the growing threat of the Imperial Japanese Navy (whom had proven themselves to be imperialists).
China does not have the same requirements. From its interests perspective, it has all the economic trading covered by the USA + Allies. All the major trade routes are covered by that.
If their interest was solely Taiwan, their force composition would be lots of littoral vessels, survivability at littoral depth, and magazine depth for localized purposes. You would see a huge uptake on LPD's and LHAs, not the 8 + 8 they have planned right now.
Instead their focus has been Escort Destroyers with huge magazine depth but high in-dock maintainence, Aircraft Carriers, Long Range Strategic Bombers, Naval Air Wings, Distance austere submarines outside of the standard SSBN's.
This suggests that their force composition is built for huge power projection.
You don't need Nuclear capable Aircraft Carriers to invade Taiwan, it's literally within continental China range. You do not need fleets of Escort destroyers for Taiwan as it falls under standard PLAAF Air Umbrellas. Etc etc.