Simplicity = Reliability
Humans are endlessly complicated, as studied through psychology, sociology, anthropology, and medicine. Within and around such complexity, we design systems and products to manage and serve our needs.
Raymond Loewy, who helped establish industrial design as a profession made the drawings below in 1933, which communicate how simplification happens over time:
With such radical complexity in our lives, a simple design that addresses direct needs is better than a complex design that tries to do too much. When something is reliable, it appears elegant and unstoppable. So, when a design is complex, refine towards simplicity to test reliability.