While the ending is certainly dark, I would point out that it was not simply that civilization was destroyed, it destroyed itself because of the values of those in charge and the implicit acceptance of those who put them there.
You can’t save someone who doesn’t want to be saved.
And that’s one place where the book was so evil. Even Eddie was left to die, because he wasn’t one of Rand’s “innovators.” Let alone that he ran her railroad for months, very successfully, while Dagny was literally just screwing around. In Rand’s world, you are either completely self-made, or you were the problem, and begging for your own death. Tell me Eddie was part of the problem. Tell me Eddie deserved death.