Simple: if you don't intend to alter the situation on the ground and commit resources to the problem: don't publicly declare the official foreign policy position of the United States to be "Assad must go" and don't follow that up with "chemical weapons are a red line." As for ISIS: don't make stupid statements (noticing a pattern here?) that they're the "JV team" when your own intelligence agencies are saying "this is something to watch and be concerned about." And above all DON'T sit there with your fingers up your azz while they're driving in massive caravans across large swaths of Syria and Iraq without an air force or ability to stop a squadron of fighters from decimating their movements. It was easy to roll them back once we brought to bear our Air Force and allied partners: why the hell didn't he do it as they were making rapid advances over several months? Could have prevented a ton of civilian bloodshed in Iraq had he done so.