Comment by dutchbart

Diagrams and really, just designing the software you are trying to build is mostly about finding out painpoints before you start the programming (at least at point the time-consuming part). The diagramming allowed you to, without programming, show interactions between modules and check on a high level if you are missing edgecases that can’t be solved because of the design. If you were just using it just to apply design patterns then you were doing it for the wrong purposes.