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As much as Gantt charts have benefits to project management, they are limited. The first limitation of a Gantt chart is that it relies upon the
work breakdown structure to have already been constructed - and for it to be complete. Should there be major tasks missing from the WBS, or should a major milestone be missing, the Gantt chart will not tell you. In fact, if you are attempting to create the work breakdown structure at the same time you are constructing the Gantt chart, you run the risk of having to recreate the entire project schedule if something is left out, a duration is mis-estimated, or another mistake has been missing.
A second limitation of the Gantt chart is that it only works well with smaller projects. Once the durations and tasks stretch past one page, the Gantt chart begins to lose its functionality. Part of the reason this is undesirable is that if the chart is more than one page, it will become difficult to view the chart on a computer screen. Moreover, the Gantt chart does not do well to depict complexities. For example if a milestone has multiple tasks required for its completion, and each of those tasks has sub-tasks, the Gantt chart cannot depict this well. For this reason, project managers should not rely solely upon the Gantt chart for project management needs.
Finally, Gantt charts do not do well with dealing with project triple constraints. The triple constraints are: Time, cost, and scope. The cost of a project is not depicted on a Gantt chart. Also, the full scope of a project cannot be depicted in a Gantt chart. No matter how detailed the Gantt chart is, the full complexity is not depicted. This is because the main focus of the Gantt chart is time.
