Agile software development acknowledges uncertainty. The ability of agile methods to make it very obvious very quickly when a project, or even a process, is failing makes people uncomfortable. The visibility of the failure leads to a desire to return to more "traditional" processes. For example, a common complaint is that agile organizations don't create "good enough" specifications. Someone might blame an unforeseen problem on the lack of a spec that mentioned it. This is possible, but it's only true if the person writing the spec could have foreseen the problem.
The desire to point back to a lack of specification also points to a lack of buy-in to a fundamental premise of agile: it's a collaboration between the business and the engineering team. Some other possible causes of the problem could be:
- The development team didn't test thoroughly enough.
- The code was not agile enough, so the bad assumptions were embedded into the code so deeply they were difficult to address.
- Communication was bad.
There are projects where things are known with enough certainty that a waterfall process can work. People can write good specs, the team can implement to those specs, and the end result is as exactly what everyone wanted. I've worked on projects where this was true, and in these cases, the specifications were reviewed and tested as much as code might.
Even projects that seem suited to waterfall fail. For any method to be successful:
- Everyone involved needs to be committed to the approach and
- There needs to be a feedback loop to correct errors in time.
The second is point is more important than the first, since people will make mistakes. But being committed to the process is what lets people accept and offer constructive feedback. The reason that waterfall projects have such a bad reputation is that many are implemented in a way that results in problems surfacing late.
Agile methods when done well have the advantage of having built in feedback loops, so that customers and teams have ways of identifying problems early. When agile projects fail it's often because people ignore the feedback and let things degrade for longer than necessary. (Failing fast can be considered success!)
So, Agile or not, your process will only work for you if everyone works within the framework to the best of their abilities, and if you have mechanisms in place to help people do the right things. Otherwise you can blame your process, but odds are, that's not where (most of) the fault lies.