There is no one "root of all evil" in software development. Design is hard in many ways. People tend to underestimate the intellectual and practical difficulties involved in building a significant system involving software. It is not and will not be reduced to a simple mechanical "assembly line" process. Creativity, engineering principles, and evolutionary change are needed to create a satisfactory large system.
Bjarne StroustrupThe most important single aspect of software development is to be clear about what you are trying to build.
Bjarne Stroustrup