Realism is Stranger Things was to evoke nostalgia. They didn't have to place this story in the 80s. They did it because they wanted nostalgia to be additional "selling point". They did it well because they knew huge part of their audience remembers the 80s and will appreciate it.

Historical movies are the exact opposite. Very few people will appropriate historical accuracy, most will not even recognize it, or worse, be confused by it. Some things we done wrong so many times people are used to it. It's also very difficult to do accurately and requires a lot of time and resources which a lot of productions don't have.

I don't even know what people are arguing here. That historical movies should all be huge, accurate productions? That inaccurate movies should come with some warning labels? Or include dragons so no one is confused by it?

Imagine I'm a beginner filmmaker and want to tell to story of Abbas ibn Firnas because I think it's interesting. I have budget for enough CGI to make Cordoba look like it's 9th century but not to dress dozens of extras in accurate clothes or film it in Arabic. What should I do? Give up because I can't make it perfect? Or tell the story as well as I can? If in the end I make a good movie and people learn about Abbas ibn Firnas from it what's the point of complaining about the costumes on youtube?

yes but the simple fact is that a movie will always be a simulacra. it’s not possible to do it any other way. those that strive for accuracy are just nerding out about a different touchpoint to the current era, in a world long gone.