I like to think about it like this. If you are building a skyscraper in Manhattan you need a plan. It has to be engineered. The materials must be specified and ordered long before construction starts. There are engineering practices and building codes that create a measure of safety. There is an order to the construction process. The project plan would likely be called “waterfall”. If you attempted an agile approach of dropping off a team and saying for our first sprint let’s just dig for two weeks, then we’ll plan what’s next is not going to cut it. Agile on the other hand is great for smaller, less complex efforts where the desired outcome is “fluid”. Different methodologies work best for different things.
All I can say is the big waterfall projects I was on pre-agile had excellent planning for the wrong things, and took up most of the time allocated for the project. So we were out of time, the quality and people suffered. Another project was cancelled because we took so long planning, the company lost interest.
