Earlier quoted context omitted.
I was once explained the interest of quick iteration cycles (the main opposition, IMO, to a waterfall model) in a simple way: The teacher drew a very simple chart : y = t. "This is, in a given project lasting from t=0 to t=1, the amount of practical information that you have about how to design this project. At t=1.0, you have 100% of the information. When you start, you have about zero information about it, just gue…
Waterfall can be fast. In fact, done properly, it is the fastest technique of them all.
"You're doing it wrong" is not a compelling argument.
A competent, motivated, invested, and empowered team don't need any particular methodology to succeed. Methodologies are adopted precisely because many people don't do things properly much of the time. A methodology which doesn't account for this and doesn't self-correct when done improperly isn't worth a whole lot.
Waterfall done properly produces great results. Agile done properly produces great results. Both of them produce bad results when done poorly. Proponents of one tend to compare their methodology done properly to alternative methodologies done poorly. That's a pointless conversation to have.