I don't think that is how the word "support" works. 5e is almost as bad as Rifts was for overflowing gonzo kitchen sink be anything screw balance or cohesion of options & when it comes to supporting settings the critical difference is that rifts owns it's overflowing kitchen sink blatantly enough that the GM only needs to say "no Bob, we agreed to play x region of the world".
The default setting − Forgotten Realms − is kitchen sink.
Other settings focus on a specific genre, theme, tropes, and mood.
It is possible to have a 5e setting where the Human is the only sapient species that exists.
Perhaps Fighter and Rogue, and certain subclasses for them, are the only classes in play.
Also, settings can diversify regionally.
I normally make the Martial power source Human and Material Plane, only. Anyone else with a Martial class needs to explain how they learned the Martial skills from Humans, directly or indirectly.
Oppositely, the Feywild is strictly magical. Its cultures are Bard, Wizard, Psion, Sorcerer, and an Ancient Oath Paladin flavor (fullcaster) Cleric.
Other classes that are present are atypical and require explanations.
Primal is also Material Plane "only", with emphasis on the
Elementals of ordinary landscapes, seascapes, and skyscapes.
Unique individuals exist. The "prominent" class options shape the culture.
Relatedly, I view the "classes" specifically as "combat styles". These class traditions evolve from warfare. Some fight with spells, some fight with swords, some fight with both. It is possible for a remote culture to lack classes because they lack a history of warfare.