The major problem was that that war was unwinnable without escalating into a US vs USSR and or China full-scale exchange. That legit concern put way too many restrictions on US field commanders, such that it was unwinable. Why waste lives in a no win scenario?

We also know now that the war was too heavily orchestrated from Washington, the military itself corrupted by stuff like faux body count stats for officer promotion, the media's propaganda onslaught picturing Tet as a massive defeat which it wasn't, the resultant hostility towards the military on the homefront, the poor morale of a drafted drug-infested army without a meaningful cause to fight and so on.

The best thing to do was to get our troops outa there although there are some recent writings which I haven't read that contend we abandonded the effort too soon. Given all the above, I doubt it.

The Vietnam debacle led to the best people in military culture re-inventing the US military and purging Vietnam era failed policies. Our armies today are nothing like those of the 7os.