Killing or capturing the Islamic State from Mosul to Raqqa, without a clear strategy for bringing about any kind of stability is as ill-advised as you say; conflict for the territory and regional dominance will continue amongst the various stakeholders. I doubt nation-building in Syria or Iraq is a top concern of the White House, yet a failed Islamic State may result in a regional war. Despite all the bluster and style differences, President Trump’s approach to actual international conflict is at the moment a slightly more muscular continuation of former President Obama’s methods to confront Isis in Syria and Iraq. Unfortunately, that approach failed to diminish the conflagration in the least, and modest escalation is unlikely to change the dynamic. It has been a long time coming for the Congress to stop being so wimpy and perform their authorization and oversight functions over the use of military force.