When we talk about achieving an Islamic state, I assume we mean both a state in which Shari’ah is implemented, and a state which enjoys some degree of power and socioeconomic viability. Otherwise, we can all move to Kandahar.
You do not achieve power and viability by destroying your own infrastructure, ruining your economy, and making your own people refugees. That is a recipe for devastation, not liberation. I am sure Shari’ah can be implemented to one extent or another among the survivors and amidst the rubble. But, again, if that is the Islamic state we hope for, Afghanistan is already available.