Robert discusses the importance of simplicity in design. He notes that trends come and go but one constant rule is to keep designs simple. Users have short attention spans of only around 2 seconds so designs need to be clean and only present essential elements. Elements like special offers and recommendations should not use up all available pixels and distract from the core user flow. Designs should use whitespace for balance, focus on the primary action, and be thoughtful about colors, options, and functionality to create an easy experience for users.