Solving Humans
Stop me if you've heard this one. You've just started a new game of D&D, and one of your players decides he's going to roll up a Human. What kind of human? Well, something vaguely European, probably. What does their culture value? Probably whatever the player does. This is a problem I like to call "Playing a Regular Person". This isn't a problem unique to Humans, but it can exacerbated by blindly picking Human. In D&D specifically, cultural aspects of other races can often be picked up through their descriptions or mechanics. But Humans are made out to be intentionally vague. There are no human subraces, no flavor that indicates a culture. But as much as you can create with a blank slate, in reality, creativity thrives on limitation and guidance. If we take a look at major works of Fantasy, this is almost never an issue. The Lord of the Rings has Northmen, Gondorians, Númenóreans, Haradrim, Easterlings, and more. Many groups of human cultures. The Le