It's all about entertainment
For all the complainers, the historians, the reality police, et al, this movie is about entertaining audiences.
All of these Hollywood blockbusters from this "golden age" were set pieces for the MOVIE STARS.
The movie is only peripherally about Robin Hood and medieval England, it's about Errol Flynn and Olivia DeHavilland place in a pretty, romantic (in the traditional sense) setting.
The whole purpose was to entertain. They didn't care about historical accuracy, they didn't care about politics, how realistic the costumes were . . . they didn't care about the details.
All of these adventure movies were made to entertain . . . an art Hollywood and the entire film industry seems to have abandoned for their politically charged, agenda driven, tiresomely didactic screeds, remakes, and comic books.