The pivotal moment in "Oh, the Places You'll Go!" by Dr. Seuss is when the protagonist encounters the Waiting Place. This is the turning point in the story because it represents a moment of decision and reflection for the protagonist. The Waiting Place symbolizes a state of stagnation and indecision, where individuals are waiting for something to happen instead of taking action and pursuing their dreams. The protagonist is faced with the choice of staying in the Waiting Place or moving forward and taking control of their own destiny. This pivotal moment brings about a shift in the protagonist's mindset and sets the stage for their journey towards success and fulfillment.