What makes you think China doesn't?
To start - The reason on the seeming boom in surface combatant production rates versus the rather dull production rates of submarines mainly lies on the fact that the required technological mastery and maturity in the domain of submarine development and manufacturing - Which can produce submarines that are near-peer (or even peer) to the current world standard - Wasn't achieved by China until the last few years. The same was achieved for the surface combatants much earlier (in the late-2000s if not early-2010s), which is why the PLAN can induct the 052D/DGs and 055s en masse since then.
If anything - The recently-completed eastern section of the Huludao Shipyard certainly isn't for show.
View attachment 154880
(Every one of the submarine + launching barge represents one assembly bay)
If anything -
Huludao alone likely has more nuclear-powered submarine assembly bays than all the other P5 members' nuclear-powered submarine assembly bays,
combined. Plus from my calculations - Should the production capacity be put into good use, Huludao can actually produce
5x nuclear-powered submarines (SSN + SSBN) per year, which is significantly higher than every other the P5 members.
This hasn't yet consider that there are two other shipyards in China that are responsible for submarine construction (Jiangnan and Wuchang), albeit they only produce conventionally-powered SSKs (thus far, for Jiangnan's case).
Also, did you miss out on the 8x 093B SSNs that were launched in the past ~2.5 years? As a matter of fact, Huludao actually launched more SSNs in ~2.5 years that they have ever been in the past 3 decades.
And with the 095-class SSN getting ready (expected to be early-Virginia-equivalent, and its iterative development in the works), we could be seeing the first 095 boats (alongside potentially the next batch of 093B boats) pretty soon.