The question of 'just' does not really apply. The effect of the Fall encompasses all. One's view rather depends on whether one holds a Latin or Greek view of Original Sin. The Latin view is that we are all culpable of the sin of Adam, therefore we are born in a state of personal sin and thus justifiably condemned before the get-go. The Greek view is more nuanced, that we are all born suffering the effects of the sin of Adam, so it's a bit like an hereditary disability, rather than individual immediate culpability. Lastly, the eschaton is not a temporal state — time is a condition of our physical universe. So 'The Harrowing of Hell' is an analogous teaching to indicate that the triumph of the Cross applies across time, rather than applying after the physical event, suggesting those who died before Christ are left to suffer.