As I said, empty filler to bind the crap together.
Even if it were filler (somehow) how does that make the plot not about Luke? If so what the hell is the plot about? I know it isn’t about blowing up SKB because that was pretty much skipped over.
Remove Luke element from the film and replace map to his place with map/blueprint of the superweapon (which is film’s defacto focus anyway) and you have completely identical film.