Just like Vietnam, the issue isn't military capacity, it's the political will to fight. The political will of the United States caused the war to be a limited one. The media played up every non-combatant death (real or imagined by the Taliban), and constantly stressed the disproportionality of the fighting. The net result was the US fighting the Taliban on their terms instead of using our full might to win. This ultimately let the Taliban hide out mixed into the civilian population, to nice their time until the US completely lost the will to fight.