Films make mistakes. Conveying something as massive and intricate as a war requires some creative license just to make the mess manageable. In reality, wars have a cast of millions and run times only measurable in years, if not decades. Add the contentious nature of historical accounts and you have a recipe begging for bias, spin, and flat-out egregious errors. So it shouldn't really come as a surprise there are so many inaccuracies about the Vietnam War in film.
Yeah, there are a lot of things movies got wrong about the Vietnam War. Even the official historical account is a matter of controversy (was the Gulf of Tonkin, for instances, a false flag operation?). Beyond the hawk vs dove bias, there are some things movies just missed, be it a minor bend of the truth or a significant alteration to truth done in the service of narrative.
Some films on this list are among the worst depictions of Vietnam in movies, steaming piles of cinematic excrement shat out by greedy incompetents hoping to take advantage of the rampant stupidity of the masses and cash a check written by misguided patriotism. Others stand among the greatest American films ever made, yet took creative liberties to service the vision of a filmmaker over strict adherence to the truth. Hell, Oliver Stone, write and director of Platoon, served in the Vietnam War, so probably knows more about it than you do. But the fact remains, all these movies fudged the truth for the sake of narrative convenience.