Calling them &quot;know-nothing&quot; isn&#x27;t criticism, rather, it&#x27;s merely to say they lack assumptions of parametric models (or that they are even statistical) and lack guarantees w.r.t. error bounds.  Whether that is good or bad depends on the goal, e.g. prediction or interpretation.  There&#x27;s also no doubt that he understands the bias-variance tradeoff... (hint: check his homepage).