They took a very philosophical book that discussed the basis for granting the suffrage on being willing to put yourself between society and the people and the dark unknown, of what any kind, by volunteering for ANY KIND OF GOVERNMENT SERVICE, at the government's need. It was your choice to volunteer.
Once you volunteered, no matter what your abilities or disabilities, they'd find a place for you to serve, whether it would be in the Mobile Infantry, piloting a starship, sweeping streets, working in an office, or being a guinea pig for a drug test, or counting the hairs on the back of that guinea pig. . . ANYTHING, so long as you had volunteered for public service. . .and fulfilled the minimum of two years OR the period of an emergency (In case of war), you'd become a veteran and receive the franchise.
Alternately, you could live in society without ever volunteering or serving and still participate in all the benefits of that society, without being looked down upon, or condemnation, except you could not ever receive the franchise to vote OR be elected to any public office. That PRIVILEGE was reserved only for those who had put their lives at risk by the mere act of volunteering and COMPLETING that term of service, showing they were willing to put society above themselves.
The movie essentially turned that into a FASCISTIC society with completely militaristic volunteering only.
The movie makers also tossed out one of the most intriguing ideas Heinlein ever put forward, the idea of the armored enhanced PERSONAL infantry suit, which the soldiers individuals wore which we are now getting closer and closer to having every day. This suit gave each soldier the ability to jump hundreds of feet, and carry tons of equipment, mirroring every movement his body made. We saw something similar in Avatar. . . but Heinlein described it much better in Starship Troopers.
They kept some of the tropes from the book, like the name of the starship Rodger Young, but dropped the use of the Song "Ballad of Rodger Young" as the means of recalling its troopers. It's a great song. Listen to the Burl Ives' version of the Ballad of Rodger Young. "Shines the name, shines the name of Rodger Young. . . " Nope, left out.
Yeah, the power suits are completely missing in Paul Verhoeven's 1997 bastardization. You would think that with the unbelievable power of today's CGI, a rebooting of Starship Troopers would be fresh meat for a film franchise that 12 to 14 year old boys would flock to over and over again.
However, considering that the Hollywood liberal elite would again distort Heinlein's story and philosophy, perhaps it is best to just keep the purity of the book close at heart and leave the rest alone.