You didn’t read it did you?
I did when if first came out, during the Vietnam war.
actully yes I did.
the main character and a small subset of humanity use time dilation to stay near the same age as the rest of humanity “evolves”
to include - Health care with a max $ output then only palatine care including “super cannabis”
The final battles against the alien race were fought hand to hand in a energy damper field of some type
The aliens “win” but mankind is now mostly clones and homosexual but and offer to “switch” the forever war vets if they wish.
One of the vets even tries a relationship with one of the clones..and found it very unsatisfying.
Finally the vets and their sig others that have used time dilation to survive get a planet.. the rest of “humanity” allow this as a thank you and an experiment of sorts.
but its been nearly 20 years and I did not like it all that much so I might have a few minor points off.
Satisfied ?