I thought "kitchen sink" meant you had everything. Science fiction, fantasy, Gothic Horror, mysteries, combat, diplomacy, guns and swords, Orcs and Xenomorphs, Psychics and Shaman and so on.

In a typical medieval fantasy setting most races are very small due to the nature of the settings being way before a billion humanoids exist on the planet. Small tribes rather than cities. It was a major deal back in the day when Orcs had their own permanent Kingdom of Many-Arrows.

One detail that is necessary for growing populations actually is peace. You need people to grow food, have children, and not conscripting farmers for campaigns lasting months or possibly years. Violent races don't have that kind of society so generally speaking their populations are very low.