HQ-19 and DN-3 are supposed to be quite decent. It didn't work for US, but US is working with higher corruption and a smaller economy.Like what star wars plan of us ?? This all abm interceptor thing sound great but has no real use in in military cuz it is unproven and experience let me tell you something 100 billion dollars for like 66 gbi interceptor which has low sucess rate do you think it is good to build such abm wall without great pain to a nation?
Barring a black swan leap, I don't think China can achieve anti-US protection level, but even an ability 1/4th of the way there will be sufficient to stop any other nuclear country besides US and Russia. All the interceptors can also be used in conventional war (iffy if DN3 works, they're huge like the GBI).
Rocketry is China's best strength, like how turbofans are US'. It makes sense to endlessly sharpen it.