...they seem to be saying that prequels are pointless since you already know what's going to happen. The point of prequels is to add to add to the characterization of a character you want to know more about. We learn that Han was once like Luke. Optimistic and looking to the skies with big dreams. He wanted to get out of this town and become the best pilot in the galaxy. It was only after the events of this movie (and who knows what else afterwards) that he became the cynic he is now.
Also, the other point of prequels is to show us the events we've only heard about. How Han won the Falcon, how Han met Chewie, the Kessel Run. Isn't one of the rules of screenwriting show it don't tell it? A prequel is the chance to go back and do that.