Agilists sometimes behave unreasonably by pummeling the Waterfall approach. Personally, I think such evangelists could better spend their effort producing solid, relevant code, but evidently they are on a crusade and need an enemy. If they need an enemy of Agile, however, they could have made a better choice.
There's nothing wrong with the Waterfall approach—if applied appropriately. For Waterfall to work well, you need to solve a problem that's not destined to change much, or, ideally, to change not at all. Some Agilists claim there is no such unchanging problem, but they're merely showing their lack of experience. I've seen a number of such invariant problems, and they yield very readily to a properly applied Waterfall development.
For example, Erik, a former student of mine, made a lucrative business of converting COBOL programs to new COBOL programs adapted to new versions of the COBOL compiler. Erik's customers wanted assurance that nothing would be changed in the conversion. This was a perfect situation for a simple Waterfall approach, one that Erik could perform profitably at a fixed price and schedule.
That said, the number of such invariant problems is not large, and it's usually difficult to know at the beginning if a problem will turn out to be so stable. In Erik's case, some of his customers would decide midway that they wanted a few "tiny" improvements in the converted application. Erik controlled that situation by charging outrageous fees for even the simplest modification. Most of us, however, try to control this situation by employing some Agile approach.
Let's be honest with ourselves: one consequence of an Agile approach is the loss of our ability to work to a fixed cost on a fixed schedule. Erik could do that, but only in a few carefully controlled situations. Many managers frustrate themselves over this lack of control and blame it on Agile. What's really to blame, however, is their inability to control the world in which they live. Things do change, and much of the time it's these very managers who instigate the change.
What do frustrated managers do? Quite often, they elevate their attempts to control the change by making rules. They may start using a pure Waterfall approach, but as their frustration with changes grows, they may add a Change Control Board, or change reviews, or a Change Tsar, or any of a number of other tactics. And, when those tactics fail to produce absolute predictability, they add more of the same kinds of rules and their supporting tactics.
After a while, these rules upon rules produce an approach that, though called "Waterfall," is actually something quite different—something for which we so far have no accurate name. This "something" is what Agile is responding to, so I suggest we name it.
What are these cobbled-together approaches like? First of all, they create a sad and dismal mood among those poor developers condemned to use them. When I visit a new client, I can generally detect the use of such an approach while I take a stroll through of the premises. I can even detect such approaches over the phone. How? Simple: the mood of my clients is mournful, gloomy, sad, unhappy, doleful, glum, melancholy, woeful, miserable, woebegone, forlorn, somber, solemn, serious, sorrowful, morose, dour, cheerless, joyless, and dismal.
That's quite a sobering list of adjectives, but that's what I can sense in many so-called "Waterfall" environments. Perhaps you recognize the list, but in any case, you can find that list in your dictionary as synonyms for the rare word, "lugubrious."
Perhaps the word "lugubrious" is unfamiliar, but that's good, because we won't often find it used in other contexts. Besides, it's a rather onomatopoetic word—a word that phonetically imitates, resembles or suggests the source of the sound or situation it describes. That's why Agile was invented—to replace those mournful, gloomy, rule-dominated approaches with brain-driven judgments of the actual builders.
So let's be truly Agile and stop bashing the true Waterfall approach. Instead, let's turn our contempt on every Lugubrious approach—or, to make a noun from the adjective, Lugubriousity. Maybe this more accurate name will help us defend our Agile projects from frustrated managers' attempts to smother us with yet more rules.
Or, to paraphrase DeMorgan, who in turn paraphrased Swift:
Great rules have little rules upon their backs to spite 'em,
And little rules have lesser rules, and so ad infinitum.
Never forget that's why we do Agile, not to dry out Waterfalls but to defeat Lugubriosity.
For more thoughs on the Agile approach, see