The Waterfall model is a linear and sequential approach to software development that proceeds through stages in a top-down manner. Its disadvantages include:
It is inflexible and does not allow for changes or iterations once a stage is completed.
It is not suitable for complex or large-scale projects.
Measuring progress and project status is difficult until the end of the project.
Testing is usually done at the end of the project, which can lead to delays and rework.
It does not account for customer feedback or changing requirements, which can result in a product that does not meet customer needs.