Am I the only one that ever gets sick to death of playing nothing but high fantasy games filled with elves and wizards???My answer is no. It no more boring than the fact that the planet Earth only filled with a single sentient species known as humans.
The trick is to figure out what cultures and sub cultures exist within your setting. That the stereotypes are just a baseline and that true situation is one of incredible diversity.
One way I generate diversity is think of the implications of the supernatural aspect of the game rules and do a what if. Extrapolating the possible effects on the different races and picking the ones that are the most gamable, interesting, fun, and fit with what I want out of my campaign.
If you have trouble doing this then have your players help by running a campaign to flesh out one or more aspect of the setting. Have everybody be a member of the thieves guild, a beggar, everybody from the same neighborhood in City-State, a city guard, etc, etc. The results are surprising and often useful as background for the next campaign. If something is precluded by the situation in the current time period then pick a time in the past and run a campaign then. Use that as background for your "present day".
Now I do run other genres and enjoy refereeing or playing them. But I stuck with the Majestic Wilderlands for fantasy games, because long ago I figured out that with a whole world at my fingertips what I can do is unlimited.