Only one team can win a SB every year and obviously QB is the most important individual ingredient.
That said when you are only looking at that one team per year in terms of how to build you're making a massive mistake.
Also I don't see why you'd ever NOT want any of your skill positions to be top players on a rookie contract whether its HB or DL.
Of course, you want to be the best at every position, but it's about opportunity cost. You only have so many picks, so it's wise to identify which positions are most and least valuable. If you chart those position out, RB is at or near the bottom of the list.