Without going into the rest of the book, there is something I always have found grating in Ben Elton's novel "Stark". Perhaps it was his intention to have it irritate, perhaps it was his way of killing everyone off...
The end of the novel is very bleak, ending in everyone dying - the good, the bad, the innocent. The way the novel's Baddies die off is the one which could seem to be, with a bit of hindsight on their part, easily prevented.
Simply, the mega-ultra-rich who are the antagonists escape the destruction that they have headed (with the complicity of everyone in the story), die by suicide. They have orchestrated a massive survival program, yet only to choose to save themselves. They take no technical personnel, no workers, no scientists, not even any entertainment people. One or two try to take people of a more... intimate entertainment strain, one even assigns a person's weight, space, and spot to his supply of heroin.
Their continued, collected selfishness fails to notice that the only company they will have are the people that they most despise - each other. By various means, they kill themselves - with the Earth dying in the background.
It's irritating because not only is it so stupidly preventable but because, human nature being what it is, it is easily likely that that would happen.
No man (or, indeed, woman) is an island. Time and time again, it has been shown that individuals or small groups have a harder time of surviving than larger groups do - particularly in harder environments. If you want to rebuild civilisation (or build a new one), you can't do it as a single person, you need a group. There is too much to do to do otherwise.
I'm slowly working on the numbers, but it could quite easily be a half to a third of people needing to be workers, entertainment, and so on, a third to a quarter scientific, engineering, and technical; the rest the traditional "upper" classes. Of course, there would likely be children - needing resources, space, education but not adding to the workforce for several years.
Case in point - farming vegetables and grains is a labour intensive process. It can be made easier, but still requires work. I've moved to growing food trees and bamboo - I don't have the time at the moment to do much more.