There really weren't a bunch of POC in Tudor England, there weren't even after England became a big colonial power. Even now, the percentage of people of African descent in Great Britain is a whopping 3 percent. I find it funny how many black actors the Brits have on their shows, while ango-Indians, who comprise a much larger percentage of the population, are still underrepresented onscreen.
One big reason there weren't more is that the cold, grey climate was damn hard on anyone who wasn't ghost-pale. There was no Vitamin-D fortified milk. One of the reasons that slavery of Africans never became a thing in New England or Canada is that the Africans didn't survive the climate. (They could and did, however, survive terrible, but sunny conditions in Brazil.)
And no one was wandering over from East Asia, which required either getting around Africa or crossing both the Atlantic and the Pacific or trekking across the deserts, steppes and mountains of Asia, to set up shop in London.
So, yeah, the historical inaccuracy is glaring. And for the person who keeps saying--oh, but what about . . . yeah, those historical innaccuracies *also* bug me. A mixed-race actress should have played Marianne Pearl. The live-action Ghost in the Shell flopped, in part, because people *were* ticked at ScarJo playing the Major. My own feeling was that ScarJo could play the Major, but if you were going to go that route you had to truly Americanize the script--in the same way Kurosawa made a truly Japanese version of Macbeth with Throne of Blood.
Color-washing is a cop-out--I'd rather see reasonably believable casting of characters like Bess of Hardwick AND a wider range of stories told. There's a real laziness about all of this and people can see straight through it.
I wish, for example, someone would do a good biopic of Josephine Baker--she was a remarkable woman who lived a fascinating life. Or, if you're feeling French, something on the Dumas father and son (mixed race). There are plenty of real stories that don't get told.