Possibly. BUT. . .
When you take all the rating services and examine their rankings/ratings of individual players, you can usually get a good idea of the player's potential. There is either a consensus or consistency except for an outlier (love that word, coined, I believe, by polling genius Nate Silver).
I have often posted my view of the combination of vital importance and extreme difficulty in evaluating individual athetic talent (hey, remember the trade of Jim Fregosi for Nolan Ryan?). This process is compounded when guesstimating how individuals will perform at the next level (remember Ryan Leaf?).
So the stakes are high and the margin for error is wide. And putting down any single rating service is as easy as catching fish in a barrel. But I contend that when viewed collectively they are useful.
Maybe.