I think a big shift in modern software development came about when people finally realized that developing software is by nature a "messy" process. Loose text files, REPL sessions filled with red lines on the console, randomly scribbled boxes with arrows on loose sheets of paper strewn about the room; traversing object graphs in your head while on the drive to work. There is no "outline" to frame any of that. The outline only exists after the software has been built.