I'm a big believer in recruiting rankings- but not for all positions. For example, I put only some stock into rankings for QB's, and as far as OL goes- I put next to zero stock in the recruit rankings for OL. OL recruiting is a complete crapshoot.
I think for the most part WR, RB, CB, and DL are accurate. Those positions are for the most part just pure athlete/raw talent/instinct. I mean anybody can look at a Clowney or Bosa or Rashan Gary and be like that's a 5* DL. Doesn't take a rocket scientist.