Well, let's check a few things. Were you aligned with them to start with? Did you know exactly what they were helping you with? Did you show up & do the work that was asked of you? Because I believe that every mentor has something valuable to give, you may not of got the “results” you were hoping for, but I bet if you sat with it for a moment, you definitely would have learnt something. If you still think, nope, then I'm sad for you!