Having an airframe where you can make ~80 special mission aircraft including 60 of the all important AEW does signify a successful platform no matter how you slice it. If the platform is bad you make a handful while researching and waiting for a better platform. You do not make 60 KJ-500s and KJ-200s if the system is not capable. Most countries have a handful of AEW, even US has half of that though its base platform is a larger commercial jet.
The Y-8/9 airframe being successful due to being the best platform available, is different to being as optimized for its role as the PLA would like (whether the special mission role or the tactical transport role).
Realistically, once Y-30/new tactical transport emerges, the question will be whether a domestic, militarized C919 variant would be ready or not in a similar timeframe.
Because ideally what the PLA would want is for a Y-30 esque airframe as a tactical transporter, while a narrow body airliner like C919 to be the basis of special mission aircraft (AEW&C, EW, MPA, ELINT/SIGINT etc)