Which of the following is NOT a complexity factor in project management?

The notion of complexity in project management often revolves around various factors that can influence the difficulty of executing a project. In this case, "simple user interfaces" is identified as the option that does not contribute to complexity.

Having a simple user interface is generally considered beneficial because it reduces the learning curve for users, minimizes errors, and typically streamlines project execution. Simplicity in user design allows for easier user interaction and can lead to increased productivity, creating a smooth experience for those involved with the project.

On the other hand, options such as extensive data ETL (Extract, Transform, Load), complex data visualization across systems, and complex data manipulation all represent situations that can introduce significant complexity into a project. These factors involve intricate processes and require careful planning and management to ensure accurate and efficient data handling, which can complicate a project's execution.

Thus, recognizing that simple user interfaces promote clarity and ease of use, distinguishing it as a non-complexity factor, allows project managers to focus their attention on the more challenging aspects of project management.