Just a few of quick points:
1. Too many people underestimate how good a system "western democracy" is..for any country.
2. But its not black or white. You can (and will) have modern democracy with many many shortcomings for a very long time...in any country. But especially in poor countries where many of its modern institutions and traditions are imported and not organically developed in-situ...but even so, it can work.
3. US policy makers seem to have tried a "worst of both worlds" approach. Cynically manipulate, bribe, kill etc..and dont do it with enough intelligence to make it work.
4. That's a case by case judgement. In the best case, the people running the intervention have to be exceptional...in many cases, one exceptional person is the key. But the US is not an ancient imperial power with personalized leadership and informal networks..its a very bureaucratic modern state. That makes one think it shouldn't have tried what its institutions are not designed to do well. But there are second best options it could still have tried. Hell, it could try them even now.
5. The perfect is the enemy of the good.
6. Afghanistan is a viable country. It is even a viable democracy, but with Afghan characteristics (which may be far from Nebraska norms..but that's their problem, why should everything be America's problem?). But it was not (and is not) going to work if the hardcore Taliban are brought into it. At the same time, keeping them out is primarily an Afghan problem. WITH American help and intelligent use of its absolutely stunning technological superiority there is no reason why an American Najibullah could not beat them back for good. Even now.
7. Underestimating the hardcore enemy and having no clear mission proved costly. Were whatever "real" aims the US had in Afghanistan too base to be publicly admitted? if so, its good the US failed. If not, why the lack of clarity? It reflects poorly on US bureaucratic decision making either way.
8. In the proverbial long run, the hardcore Taliban are just a tool and not one that will last forever or work too well. If not the US, then China, or Russia or Iran or India..someone will help other Afghans cook their primitive goose. Their more modern backers, cough cough, were a different issue. They could have been convinced to let them go if the "convincers" were surer of their own ground (I am not convinced of the theory that the convincers have secret malevolent intentions that are very different from what "we" are being told...I think if they were that kind of evil genius, we wouldnt be having this discussion...but then again, how would I know?).