You obviously know nothing about film or fiction. That movie is one of the best that Scorcese turned out - a NYer who knows his history. I don’t watch Eastwood movies.
Not even in the upper half.
Then I suggest you watch the movie for it's acting and it's direction, but not for it's history. Which is why I watch "Lincoln", as well as "Goodfellas" and "The Departed". I like Spielberg and Scorcese but I don't look to them for my history lessons.