On a personal level there are many different feelings and views, most of them mutually exclusive.
On a philosophical/intellectual level I fully understand that you don't 'buy' military/political victories with a one-off cost in blood and treasure, you just rent them, and you can keep them as long as you keep paying whatever cost in blood and treasure your enemy charges.
we have an interesting parallel that no one really questions - the Falklands. The war was fought and won 40 years ago, but we still keep a garrison there in order to maintain that outcome. It has a cost, both financial and human, and we accept that.
I'd say there's little real surprise at the end result, but the speed of it is stunning, and the 'what was it for?' stuff has filled my WhatsApp all weekend. its emotionally devastating, and its wrapped up in absolute horror at what's happening to our interpreters and Locally Employed Contractors, many of whom we had really close relationships with, and who we see being left to horrific deaths - at least in part by government indifference and incompetence.
There's some real soul searching going on, and lots of utter fury, including at a senior level, and lots of it is in public.
Existential crisis is perhaps taking it a bit far, but not by much.