THE MOST IMPORTANT GOAL IN DESIGNING SOFTWARE IS UNDERSTANDABILITY

Summary from the TLDR Web Dev newsletter

The most fundamental goal of software design is to make code understandable. Understandable code is needed for correctness, security, and performance, as a lack of understanding leads to defects, security issues, and misguided performance optimizations. Focusing on understandability means making the code itself readable and providing supporting documentation to clarify complex concepts or system architecture.