I'm guessing you have never read any of Heinlein's papers - and if you read the book Starship Troopers I suggest you read it again. Along with all of his work not tagged as "Young Adult". You might not agree with him but he was writing stuff that was unthinkable at the time.
Military participation was not the the road. It was _one_ road. Other forms of service existed and anyone could start as it was a legal requirement. There was, in the book, no war when Rico joined. The key was danger in service, and the war started while he was still in service. His father was a successful business owner was adamantly against Rico joining the military.
Heinlein also discussed a female only government in other writings (his conclusion was something along the lines of "it can't be worse than the mostly males ones, and it might be better") and in Stranger in a Strange Land manages to break every single social taboo of the day. In the Moon is a Harsh Mistress he describes what stable poly relationships would look like and how living in a hostile environment with a scarcity of females enforced social order.
He also gave a KGB officer a lecture on why communism was bad while in Russia in 1960 when the U2 spyplane was shot down, translated by his wife (who had learned Russian from tapes over 2 years at home).
Basically, you got what you wanted to out of the book, but I would suggest that you didn't get the actual book.