UX / HCI
What do your users want? How can you be sure? Are you solving a real problem? Can you do it better?
A decent UI is table-stakes. User Experience is the practice of understanding not only what your product does or how it looks, but how it fits into the lives of the people who are making use of it. What problem are you solving for them? What is their context? How can this be made easier? Should it be made easier? Is friction always a bad thing? What scares your users? What makes them happy?
Design is a practice and not a particular playbook or set of techniques: it requires a good sense of intuition informed by theory and experience.
In addition to running standard design sprints, helping individuals and organizations make sense of their ideas and teaching the principles of design to students around the world, here are some examples of problems I have recently helped solve: