Not kill, because it cant kill it, more like continue to drown it, keep it weak. Pakistan doesnt want a functional Afghanistan, a Afghanistan that may bring up the legitimacy of the Durrani line, etc. A strong Afghanistan that may align with India. For that, it'll continue to meddle in Afghanistan's affairs. It's no surprise Afghans cant stand Pakistan.
you are absolutely right, why would Pakistan want a functional stable Afghanistan with open borders who is so chumy chummy with India. the day Afghans understand it will be the end of their problems., but they lack the brain and we lack the sympathy