The new shipyards are the mega sized ones designed to pump out ULCCs, Valemaxes, mega tankers and the like. These ships are far too big to be built in traditional facilities.
With that, the older, legacy shipyards are left to build much smaller vessels, including warships, Coast Guard, ferries and so on. They also do the repair and refit of the warships.
There are only a few, very few of the new mega shipyards that is used to churn out the PLAN warships. And you already saw them --- the ones in Dalian and Jiangnan. There is plenty more that don't build warships, but large commercial vessels. Warships only comprise of a tiny faction of China's shipbuilding output which is in anywhere from 35 to 45 million DWT annually.
Going back to the destroyers and frigates in maintenance, I see often wrappings around the secondary radars. These instruments are subject to mechanical wear and tear and there are both scheduled and possibly unscheduled visits that require their examination, lubrication, removal, overhaul, repair or replacement. All that trouble can be saved with digital, solid state phase arrays at the expense of a higher initial cost.