Both of you espouse a simplistic approach - must defeat ISIL and Taliban.  And this achieves what?  We have all but defeated ISIL now in terms of denying them territory.  So what?  We know that the ISIL ideology will just spread underground - we live in a post territory only world.
You skip over the actual history with US involvement in Afghanistan......we went in after 9/11 using small special forces groups that then aligned with local forces.  It worked extremely well until Bush and company moved on to the Iraqi invasion and gutted US Afghan efforts, resources, etc.  It became a secondary battlefield - here is where we went wrong.
There is no equivalency between Afghanistan and Iraq or even Syria.....every situation is different.  Iraq is challenged by two major Muslim religions;  Afghanistan is a nation in name only - significant numbers of tribes dispersed across significant geographical barriers.  Add in the continued Pakistani support or turning a blind eye in the FATA.