Originally Posted by Geist
Yet, plenty of games have taken up these themes and been reasonably successful.
Morrowind was set in a land in the throes of religious strife, whose citizens relied on slavery, while themselves suffering under the yoke of military occupation. It even featured a monopolistic 'corporation' that was corrupting local factions in order to secure exclusive access to valuable natural resources. These are heavy political themes. The Gothics and Fallouts have ventured into similar areas.
A game doesn't have to take place on 21st or 20th century earth in order to deal with difficult issues that humanity has had to grapple with for millennia, that we face today, or that we might have to tackle in the future.