I understand your point. You're right that they need more big warships for deterrent purpose. But don't underestimate the quality of the manpower. A 051B with elite and experienced crew can beat a 052D with green recruits. The arrival of the 052D in China doesn't mean that their older ships (Sov, 051B, 051C, 052B, 056, 054A, 052C) are obsolete. These older ships still capable to give tremendous deterrent to the neighborhood.
So why do they need to hurry the production / fitting / training, etc the 052D? There are another projects that need more attention too in the fleet. Like the 055 cruiser.