When management styles change or methodologies evolve we cannot forget where the methodologies or management styles came from. The old styles and methodologies worked, we want to continue doing what works and replace what doesn’t work.
When everything is thrown out we end up with a pendulum, where the pendulum swings to one side, we use one style or methodology, then the pendulum swings the other way and we go back to the older way. When we remember where the methodologies and styles came from, we get an upwards spiral where we are always getting better.
When adopting agile we can’t forget about waterfall. There are some areas where waterfall works. There are parts of a project where it is better to approach that part as waterfall, and others parts as agile.
Waterfall works in well-defined projects. When I worked on the roads, it was very much a waterfall project. They determined the requirements, designed the road, executed, tested, and completed the building of the road.
Agile works when the project is innovative and you are looking for creative new solutions that were not there before.
No project is at either of these extremes so there is a need for a bit of both on every project.