Historical parallels are over-used, and often misinterpreted.
South Vietnam fell to an invading army, which we could have stopped militarily if the political will had been there and the American people had actually supported that; neither was the case. The ARVN, at least in significant parts, fought until the end, if finally ineffectively. But they held for almost two years without US ground troops, giving Nixon and Kissinger their “decent interval” before it was over.
Afghanistan, despite many Afghans joining our efforts, just fell apart. “Nuking Hanoi” was never an option; there was no Hanoi. Most of the Afghan security forces, which outnumbered the Taliban 6 to 1 or so in nominal strength and were much better equipped, seem to have made deals of surrender or just gone home. There was no Battle of Kabul.
So all the tough talk is cheap, but also detached from practical reality. The deal with the Taliban about the evacuation seems to have largely held, to the displeasure of the Islamist Jihadis, as the bombing shows. Anyone who thinks some kind of heroic fighting withdrawal would have been preferable should study the history of the British retreat from Kabul in 1842.