No one is saying that all 4/5 stars are long time NFL players. That being said I would be willing to wager that more 4/5 star athletes get a shot at the NFL vs non-4/5 star athletes.
Look at the schools putting people consistently in the NFL, these are often teams with the most success and teams who recruited well. Do you see a trend?
Rankings are not perfect, good players will be mixed. If you have the magic sauce for college recruiting please call Saban, Meyer, Dabo and other top tier coaches and tell them to stop recruiting 4/5 star guys and focus on the 2 star athletes "who are the back bone of the NFL". Don't kid yourself, rankings do have some validity (not perfect by any means) but helpful.