tl;dr: Domain expertise dramatically improves LLM output quality: Terence Tao's ChatGPT conversation about the Jacobian Conjecture shows how an expert can steer the model into concise, technical mode, push back on wrong answers, and extract insights a novice couldn't. The key skill isn't prompt engineering tricks but actually understanding the subject well enough to identify weird outputs, suggest alternatives, and ask specific questions. This suggests humans remain the bottleneck for many tasks—the knowledge is already in the model, but it takes expertise to pull it out.