Is there any point producing a well researched history/period drama if the casting is 21st century inclusive?

It’s surprising that people become so hysterically upset about [b]fictional[/b] characters being portrayed by diverse actors (as opposed to historical figures like Obama and Zelenski). I know that meme is satire, but in the United States, for the first 50 years (at least) the movie industry used only white actors and actresses to play Asians, Latinos, Native Americans, even black characters (using dark makeup)—and little was said for most of that time. And they often portrayed people who [b][b]actually lived[/b][/b]
(John Wayne played [b]Genghis Khan[/b] ?!)

Is it that people today just don’t [b]know[/b] this history ?