Mager and Pipe: is it actually a skill problem?
Mager and Pipe, 1970
Robert Mager and Peter Pipe wrote a short book in 1970 with a single very useful question at its centre: is the person not doing this because they cannot, or because something else is in the way? If they cannot, training might help. If something else is in the way, training will not.
Their best-known test: "Could they do it if their life depended on it?" If the honest answer is yes, the issue is not skill. It is the setup around them. Expectations are off, the tool is broken, the reward structure is upside-down, or they only do it once a year. A course will not move any of that.
If you like flowcharts, Cathy Moore's Will training help? flowchart is the modern, visual version of the same idea.