Where did you get all those ‘rules’? Shakespeare’s History plays certainly don’t follow them. Neither does ‘The Three Musketeers’. Or Amadeus. ‘The Scarlet Letter’ is a great novel but is a highly inaccurate portrait of the Puritans. As for ‘The Great Gatsby’ with Jay Z music I humbly direct you to the 1944 film ‘Meet Me in St Louis’, set in 1904 but features Judy Garland singing The Trolley Song...a 1940s style big band number.
History texts are so messed up with modern interpretations. I would hope that novels, movies, TV etc that pass themselves off as based on history do their best to get it right.
No one takes Shakespeare’s “History” plays as serious history. Alexandre Dumas’ butchery of history was well known. Nobody ever claimed he was writing history, either. As for the use of cultural anachronism, it may seem artsy to pretentious morons, but to most people it’s just annoying.
You are arguing for what, unfortunately, is the status quo of Hollywood historical fiction. But just because something exists is no recommendation. Grania is arguing for what should be. I agree with Grania.