>>17981324
>Historically, is a multicultural society better than a homogeneous one?
They have advantages and disadvantages, but generally as a rule of thumb they are often more difficult to govern and have more inequality when there isn't either a strong and impartial centralized authority or dynamic federal system. Probably the best example of a dynamic, federal multiethnic state would be the Persians, who pretty much pioneered the concept of a federated empire and state structure. But then you have more conventional and recent examples like Russian Empire/USSR, Austria-Hungary, and the Ottomans that are the former, which usually balkanize and fall apart violently whenever said authority grows corrupt, weak, or falls due to war or revolution.
>>17981336
>Singapore is living proof that societies function effectively only when they are heterogenous
Singapore is a highly authoritarian city-state ruled by an impartial, centralized authority with a commerce-based economy. That's effective on a city-level, but for a national level you most often end up with cold, relatively incompetent, corrupt authoritarian regimes like post-Soviet Russia or a lot of the Arab dictators (Sisi in Egypt or the Gulf Arabs being good contemproary examples).