This is really a variation on Trump's Immigration dodge. Decapitation strikes just another dodge of the hard but far from impossible task of defeating ISIS.
Bill Roggio writes,
US continues to rely on tactic of decapitation vs counterinsurgency
The targeting and killing of Sandhere and Nabil highlights the US government’s abandonment of counterinsurgency to fight the spread of jihadist movements throughout the Middle East, South Asia, and Africa. President Barack Obama ordered the withdrawal of US forces from Iraq at the end of 2011, and will reduce the number of US forces in Afghanistan to under 10,000 by the end of the year. US troops in Afghanistan are in train and assist as well as a counterterrorism posture, and are not dealing with the Taliban as an insurgent force.
Instead of fighting the jihadist groups on the ground, the US has primarily relied on airstrikes, and in many cases, unmanned aerial vehicles that are more commonly called drones, to target senior and mid-level leaders of the jihadist groups. This tactic has been used against al Qaeda, the Taliban and allied groups in Pakistan since 2007, al Qaeda in the Arabian Peninsula in Yemen since 2009, and Somalia since 2006.
While the airstrikes have killed some top leaders in the Islamic State, al Qaeda, the Taliban, and other organizations, they have not stopped the spread of jihadist groups across Middle East, South Asia, and Africa. Nor have they denied these groups territory, which is crucial for the group to train fighters, maintain local insurgencies, and plot attacks against the West. Despite years of airstrikes against al Qaeda and its allies, and more recently the Islamic State, the groups still control territory in Afghanistan, Pakistan, Iraq, Syria, Yemen, and Somalia, and they are waging active insurgencies in Nigeria, Mali, Egypt, the Caucasus, and elsewhere.