No hint of Sexism? Women were officers only, and the big bad troopers had to stay in their own zone in the ship away from them
I'm not entirely convinced that military service is a good way to make men of callow boys. If you live in a society that demands "government service" to get the franchise it might seem like a glorious option to a callow youth. I'll concede it wasn't a classic fascist government in the book, but it certainly wasn't a democracy.
Our hero got to kill aliens and "come of age" pretty much as in the book, just without power armor. The book had quick military trails, and the scene were our hero faces "administrative punishment" instead of being drummed out of the service is straight from the book. The leadership in the book underestimated the "bugs", and I do not think they were portrayed as "clowns" in the movie.
The movie did a good job of showing the horrors of war, for example, the crew running about terrified in the ship that broke up - not calmly and heroically dying. War is gory. War is horrible. War should be a last resort.
But I certainly think the movie can be seen as you see it, given its much different tone, and obvious elements of satire where the book was much more earnest.