If your point is that these practices have ended, you're mistaken. If it's that the moral standards that led to their condemnation are a recent development, this is also incorrect. For example, the idea that slavery is abhorrent can be traced at least to the mid 1500's, when
the first laws prohibiting it were issued. It's true that the terms "genocide" and "ethnic cleansing" belong to the 20th century, but that's no reason to avoid using them to describe earlier events and policies, any more than it's inaccurate to say that Leonardo Da Vinci designed the first
machine gun.