In a best case scenario, the resistance will dislodge Haik's regime, but then what? Windrip's regime gutted the educational system, burned books, and suppressed any real high culture. The result is that youth and young adults have no background in history, literature, civics, or world events. How on earth will Americans rebuild their country if a large chunk of the population is poorly educated, with no sense of what a democratic government even looks like? The danger of demagogues and/or foreign governments taking advantage of the situation would be great.
At the end of the novel, Doremus disseminates information to dissidents as part of the resistance against the fascist regime. He's far from his loved ones and is constantly on the run to evade Corpos. When readers remember that (1) he will be doing this for a long time because it will take years to overthrow the regime in a best case scenario, (2) he's old and may not live long enough to see the regime end, and (3) the chances of him being killed by Corpos are high, it's depressing to realize that he will probably never see his loved ones again.
Several times in the decades since this book was written, America has started down the very same path described in this book. So far, the American public has come to its senses each time, before reaching the point of no return. So far.