I 100% agree and it's only natural, the authors being from different generations. Henlein was a desk warrior in the US Navy as well so he never saw actual combat, only read and heard about it, which definitely influenced his thinking and shows clearly in his early books, whereas Haldeman served as a combat engineer in the US Army and was wounded in Vietnam. Of course, the different sociological and political discourse around WW2 and Vietnam affected both. Haldeman has gone on record saying that he didn't write
Forever War as a rebuttal to
Starship Troopers, he admits he was influenced by it and it definitely shows.
the Old Mans War series
Yeah, Scalzi is definitely one of my favourites.