I found “Apocalypse Now” to be a bloated mess, and “Full Metal Jacket” ridiculous. There was an authenticity to “Platoon” that may well have been due to Stone’s combat service in Vietnam, which - needless to say - neither Coppola nor Kubrick shared.
Apocalypse Now, Full Metal Jacket and Platoon are all anti-war movies that highlight dehumanization. And all three are authentic.
However, neither Apocalypse Now or Full Metal Jacket came across as an anti-American. Platoon came from the mind of a true anti-American film maker who hates this country. A real scumbag. That doesn't seem to effect your praise of Stone. Whatever.
Frankly, I find movies more enjoyable when they have a surrealistic streak running through them. Which is why I found the Coppola and Kubrick films so entertaining. If I want realism, I'll watch a documentary.