When you study game design, you usually focus on documents and prototypes for small games. The first steps that are taught in educational centers are purely technical.
Then you are in the market without the skills that make you a professional designer. Which are not the techniques, but are those oriented toward the video game business.
Normally a team reports to one or more managers who maintain a business vision. Our role as designers is to understand how to realize this business vision. We have to think more about endorsing the product than creating something directly. Players will receive the product packed and polished. Technical skills are important, but our ability to understand the business is critical.
Personas are one of the methods that allow this communication across the whole team. I share with you this workshop that aired last Saturday. The audio is bad, but the content is excellent.
If you want to work for companies as an employee or consultant, you need to come up with frameworks that solve concrete business problems. Thinking about who will really play and how to structure a product for them requires effort and is not intuitive.