The problem is that we’re fighting this the American way. If we had fought this the Afghan way, the war would have been over a couple of years after 9/11. Of course, a few million Afghans (with a 1 to 10 or lower Taliban to Taliban civilian supporter ratio) would also be lying in mass graves. Unfortunately, to defeat an enemy that has been defeated conventionally, but won’t surrender, you cannot apply the Geneva Conventions to them.
The problem is not that we can’t defeat them, but that we won’t take measures that have worked in the past, continue to work in the present, but are now interpreted as cruelty for the sake of cruelty. They are not. We have devoted hundreds of billions of dollars towards fighting the Taliban our way. It can’t be done at a reasonable cost in American and friendly Afghan lives, never mind money. The Taliban and their civilian supporters must be slaughtered root and branch.
The hard truth, isn’t it...
You have defined the problem correctly. And, unfortunately, the reason there will be no solution. We simply don't have the will to vanquish our enemies.