I'm still undecided about the title of this movie. It comes right out and says it's about Jesse's assassination, and it tells you who did it, and so as soon as you meet each of those two characters and in each scene where they are together, your mind can't help but wonder if this is the "The Scene."
You've put your finger on the generational divide of this film, Austruck. Old folks like me grew up hearing about Frank and Jesse James and the Youngers and the Daltons and Billy the Kid. We've seen Jesse portrayed by Roy Rogers, Clayton Moore, Wendell Cory (in Alias Jesse James 1959, in which Jesse on a trip back east buys a life insurance policy from Bob Hope), Tyrone Power, Robert Wagner, Robert Duval, James Keach, Audie Murphy, and others.
In my day, everybody knew who Jesse James was, how he rode with Quantrail in the border wars, turned outlaw with Frank and the Youngers, survived the bloody shoot at in Northfield, Minn., in which the Youngers and other members of his old gang went down, and finally was killed by Bob Younger, shot in the back of the head while hanging (or dusting or adjusting) a picture on the wall. No matter what the title of the film or how they changed the plot, people of my generation knew the facts about Jesse James.
But you younger folks do not. Not your fault; it just isn't an area of interest to you.
However, it puts me in mind of a newspaper cartoon back when
Titanic was king of the box office; the cartoon showed a middleaged couple standing in line for tickets and the man says to his wife, "I hear the special effects of the ship sinking are really spectacular." Behind them in line is a group of teenagers, one of whom says, "The ship sinks? Well, thanks for spoiling the movie for us!"
I too think this film could have used a few nips and tucks to keep the pace moving. In some cases a movie can slow things down in order to create tension, but in this film that didn't work. It just felt slower.
I agree that the film could have been tightened, but I don't think it was building tension so much as providing color and historical background to new generations who don't know diddly about Wild West outlaws.