"Exploitative", to me, means that they're using you or your emotions for a purpose, notably a purpose that you don't approve of ahead of time, or that they are using people without their consent in ways they wouldn't want. (That's a tricky question, when so many of the people being depicted are dead--but we don't assume that anything about Abraham Lincoln, or the First World War, is necessarily exploitative.) Tightening the plot, or making the actors more attractive, is something that movies do, in the same way as written narrative tightens dialogue (removing the "ums" and such that are a large part of actual conversation).

Also, I gather that it isn't entirely fictional--I don't know how close it comes to the true story (and doubt I will go see it), but it is connected to events that actually happened.