The CIA were happy to supply hundreds of millions of dollars in arms to the mujahideen during the 1980s. The US chose to support Islamist insurgents in a proxy war against the Soviet Union and the Afghan people have paid the price for that decision ever since. Many of the American soldiers who died in the war in Afghanistan were killed with weapons that were bought and paid for by their own government. If you believe that the American invasion of Afghanistan was a humanitarian gesture, you have been given an extremely narrow understanding of history.

https://en.wikipedia.org/wiki/Operation_Cyclone

While this is true, it's whataboutism. You can be fixing a fuckup resulting from your government's previous actions, but it's still fixing it.

It sure seems to take a long time to fix things. Maybe fixing things at the point of a gun is the problem?

...except that now (at least AFAIU) we're backing out of those areas and the Taliban are right back in control. Maybe that military-intervention-as-societal-revenge-plot wasn't so helpful?

Precisely because the war wasn't finished... political pressure led to the military being recalled and this is the outcome. Rebuilding a nation does not just happen in a few months, it takes decades of peace. The biggest problem is the lack of commitment, due in part to a public that has lost touch with what conflict is and the will it takes to fight.