theme for a fantasy campaign

[Astromancer]

In several Old AD&D supplements (dealing with the Gods of the Demi-Humans and the Orcs) the idea of Humans as the lucky sepcies that can live anywhere is mentioned or used as an origin element.

Try this idea. It's not a blessing, humanity, traditionally depicted as less magical than the other Races, has no special home, no place that is properly and rightfully theirs. They aren't cursed, but they primal parents of humanity failed to show up for the blessings, so they don't have them.