Would like to point out that the maintenance requirements for single engine aircraft like the J-10 are significantly less than the requirements for full size twinjets
Intercepting cruise missiles with cheaper aircraft with larger payloads due to not requiring internal bays is one of the many reasons the US is still buying F-15EX. Modern cruise missiles already have ranges measured in the thousands of km, and they can be launched from submarines or other platforms that J-20s will not be able to "push outwards". The idea that the J-20 or any aircraft is able to put up some imaginary non-porous net that completely prevents aircraft from launching munitions that would need interception is ridiculous.China likely is losing the war if it needs J-10/J-11 to intercept cruise missiles. It's more about winning the war rather than optimizing a losing situation. You ideally don't want US cruise missiles to be within interception range of short-legged J-10s, because that means your J-20s has been pushed backwards into mainland. J-20's brings fight is thousands KM away, and push US assets outwards, outside the range of cruise missiles, obviating need for cost-effective interception to begin with. It's like a solution looking for a problem - if you already push US out of cruise missiles range, why do you need J-10/J-11 intercepting cruise missiles. (J-16 better suited anyways)