That makes absolutely no sense and fails as an argument. The Force is fundamental because the entire story would literally not work if it were removed. One of the most important parts to the original trilogy is "Luke learns the ways of The Force and becomes a Jedi Knight." The Force and the Jedi who use it, as a mix of both magic and martial arts, are what separates Star Wars from basically every other sci fi/sci fantasy story ever made. Nothing else in Star Wars is truly unique to it--except for the light sabers, perhaps, but I'm pretty sure that there are other space operas or planetary romances with swords. Lots of sci fi settings have aliens, spaceships, FTL drives, hives of scum and villainy, intelligent robots, totalitarian empires, good vs. evil morality, etc. Even psychic powers aren't really unique in SF, but the Force-using space samurai are.
If slavery were removed from Dark Sun, there are still many, many things that set it apart, and slavery isn't unique to Dark Sun like The Force is unique to Star Wars.