In the interest of time, for now I'll address just the "institutional" aspect of your post. With all due respect, it seems to lack an appreciation of the very wide and deep experience our federal government has with AFG by now. 20 years is a long time. The mid and senior levels of the U.S. military (including intelligence), non-military intelligence, our diplomatic corps, etc., etc. are absolutely chock-full of LOTS of folks with LOTS of experience in Afghanistan. Some of them may not be smart, might be (far) too ambitious/careerist, too dishonest, etc., etc. But they truly have "Been there, done that," often many times. So they're not ever close to utterly dependent on what any given person or briefer is telling them about AFG at any given moment. And in the defense of many, it's not even close to all about "lying." In many, many cases it's about being hopeful that SO much effort and goodwill (and indeed, billions) could create functioning state - however naive or ignorant that might appear.
That Marine Captain's view is certainly worth something. But tens or hundreds of thousands of people with as much or more AFG experience might not agree with him. In the end, of course, it's about the quality of the argument.
FYI, I served in the military for about 30 years, and did 3 tours in AFG. All of us should be plenty modest about whether or not we have the answer.
Lastly, more broadly, even if we deluded ourselves and/or misled others for far too long about our ability to build AFG, it does not necessarily follow that we should have pulled out. We could have stayed there for reasons (e.g., counter-terrorism) having nothing to do with establishing a sustainable AFG government/military. In fact, I'm pretty sure that's exactly what Biden endorsed back when he was VP. But that seems to have morphed into "Get out entirely."
To see all of that blood, sweat, tears (and indeed, billions) UTTERLY gone in the matter of weeks is profoundly sad.