When you live in a different country, you are surrounded by cultural norms of your country and disobedience is punished too (usually much more harshly than in the US). Your assumptions about actors' skin colors are as much influenced by the culture of your country as they are influenced by the US culture in the US, as evidenced by the phrase "the opinion is pretty much universal among my family, my friends, my coworkers." Please don't conflate a view from your culture with nebulous "obvious objectivity".
> making them play main roles in historical movies doesn't repair any injustices made to them.
It does not repair injustices of the past, but it helps fix the injustices of today: non-white actors of today should not be kept out of movies just because of a specific historical setting.
Any historical movie is just a modern interpretation of true events. There is no actor that can be a completely authentic reflection of a historical character. A respectful, non-mocking actor play by a person of different race can be a good reminder of that.