It must have looked good on paper, For 83 he's amazing

An actor never knows what the finished product will look like, many times they'll think they're in a flop to be surprised to see the movie become a hit, and visa versa. To me it's just amazing that Duvall can act as he does at 83, other actors like Jack Nicholson have had to quit at a younger age because of health problems or no longer able to remember their lines. The movie suffered from unrealistic settings, that I'm surprised that an actor with Duvall's range of experience and influence didn't step in to help set it on course, but he is 83, he may just have enjoyed the acting challenge.
The more unrealistic scenes to me were: Red getting tossed out so gently from the bar. I can hear the director saying, "be careful now when you take Mr. Duvall out," they should have used a stunt double. Then to have a 42 year old woman, falling for an 83 year old, needed a little more work or set up to be believable, although in real life Duvall's wife is the same age as the actress who plays his love interest, but in real life the attraction is that he is Robert Duvall millionaire movie star. I think a better set up would have been that she was being insulted by the bar patron and then Red steps up to defend her honor, and then gets beat up and thrown out for her. Next biggest one is the whole bad guy and the kid confrontation, one could still stretch believability perhaps and accept it, but then to have the bad guy get knocked out by a plaster statue arm, long enough to be arrested the following day by the police, just too much to buy. And the first bad guy being so bad but then after he's wounded seeming so sweet, and resigned to just die, wherein truth he would have had them take him to a vet at least or kept the woman or Red as a hostage until they brought him a doctor, and to leave the second bad guy alive where he can come after them later is also a possible loose end. And then the kid goes back to Texas at the end empty handed, his dad had died, he's got no money, and he had to drop out of school. Grandpa should have dropped 50G's at least, saying something like, "here kid, buy a new hat!"