Yes.. 5-star recruits are amazing, the best, and will probably get into the NFL.
But how do you get to be a 5-star recruit? You have to get an offer from Saban, Meyer, Dabo etc!!! The offers you get make your star ranking.
Coaches do not care about rankings... Coaches care about the athletic ability of the recruits and their school's current needs.
The ranking system is for the fans.