Between this thread and the erosion of racial distinctiveness post-Tasha's, I'm toying with a "Wild Cards"-like setting in which all the non-human races are humans who have survived but been changed by a magical disease.
There are different nations and cultures, but they are not built around race. "Changed" humans, whether elf, dwarf, halfling, gnome, dragonborn, tiefling, tabaxi, shifter, warforged, centaur, satyr, triton, loxodon, kobold, orc, goblin, or whatever, are a known quantity and are tolerated - or not - based on culture and individual preference.
With this, the default response to a player asking, "Can I play Race X?" is, "Sure, you got changed by the disease."