I'm sympathetic to why we all left and that the Afghans were hopeless etc.
But there are issues with the decision and I prefer to examine them rather than accept answers to questions that aren't the ones that matter. This is a least-worst scenario. There are bad consequences with every choice, and the choice Biden took has risks and costs attached to it.
1. In my view, the original US mission was met because we (the US and its allies) rid Afghanistan of the Taliban and maintained a presence there that stopped them from returning to power. It isn't met by returning Afghanistan to the condition that caused the trouble in the first place.
2. AQ is not a thing that gets to be over in the way he describes. If you let it have territory it will metastasize. It's like cancer that way. So we just gave them a host country again. They will be so happy to have the Taliban back in Afghanistan. What's the plan to deal with that?
3. We (the US and allies) haven't been losing many lives (11 in 2020) or spending lots of money in Afghanistan recently. That's an exaggeration. The annual cost of staying there was tiny. The large chunk of the cost was years ago. The US had a very small number of troops there. As did we.
4. It's not a risk-free choice. We are risking another 9/11 to avoid these occupation costs.
Biden misrepresented the context and framed answers to the wrong questions in order to make his decision seem better than it was. Nevertheless, I understand why he made it and think one can argue it was the least bad one available. But it was still a bad decision, even if the other choices may have been worse.