How incredibly good is this movie?
Ok in 1990 Costner was still a decent actor, but he's not the greatest artist and this is his first (and best) attempt at directing.
Yet it is a masterpiece of filmmaking for the ages.
I cannot imagine many ways to improve it, it's engaging and enjoyable from start to finish and excellent in all its parts.
I think it's incredibly good, maybe it was beginner's luck but it's one of those rare examples where everything magically falls in the right place.