What is the biggest gap between knowing about Artificial Intelligence agents and actually using them well?

The more I work with Artificial Intelligence agents the more I notice that reading about Artificial Intelligence agents and building workflows are completely different skills. I have seen people who know every framework and can discuss the latest research but when it comes to creating an Artificial Intelligence agent that reliably solves a real problem they struggle. Then I have met people with less technical knowledge who consistently build practical solutions because they understand how to structure tasks and iterate. I recently completed an assessment on AISA that focused more on reasoning than memorized knowledge and it got me thinking about how we define Artificial Intelligence proficiency in the first place. For those building production Artificial Intelligence agents what skills have actually mattered the most in your experience? Is it design, planning, tool use, evaluation, debugging, domain knowledge or something else entirely? I am curious whether other people have noticed the disconnect, between theory and real world execution of Artificial Intelligence agents.