The Waterfall model is suitable for ordered and predictable projects in which all the requirements are clearly defined and can be estimated accurately, and in most industries, such projects are dwindling.
Changing requirements from customers have led to an increased pressure on businesses to adapt and change their delivery methods. Agile projects are completed in an iterative manner wherein the functionalities with the highest business value are completed first. Various cross-functional teams work in parallel across Sprints to deliver potentially shippable solutions at the end of every Sprint.
As the customer regularly interacts with the team in Agile projects, the work completed is regularly reviewed; thus, there is assurance that the progress is per customer specifications. Because each iteration results in a shippable solution (which is a part of the overall product), there is a measurable objective that the team has to accomplish, and this ensures that the team is progressing and the project will be completed on time. However, in Waterfall there is no such interaction as the work is carried out in silos and there is no presentable functionality until the end of the project. Traditional methods do not present such timely checks and, therefore, result in situations in which the team might get off schedule and end up with a lot of work toward the end.
However, when completing simple projects with well-defined functionalities, and when the team has previous experience completing such projects (therefore, estimation would be accurate), the Waterfall method can be successful. In complex projects, in which the customer is not clear about what the end product will be and, therefore, the end product functionality keeps changing, the iterative model is more flexible in ensuring that these changes can be included before the project is complete. The Waterfall method struggles to accommodate such changes.
Agile methodologies require a change in mindset from traditional methods. The central focus has moved from the scope in Waterfall methods to achieving maximum business value in Agile. While in Waterfall, cost and schedule are altered to ensure the desired scope is achieved, in Agile, quality and constraints can be altered to achieve the main objective of attaining maximum business value. Agile methods are more successful in the current market, which is marked by unpredictability and volatility. Agile methods are based on inspect-adapt cycles as opposed to the command and control structures of the Waterfall method.