The right combination makes the difference
For companies, agility in its purest form is more of a theoretical construct than a real-life approach. In day-to-day operations, a balance must always be struck between the benefits of agile software development and the need for planning certainty. It is therefore necessary to combine the benefits of agile software development with planning certainty. Agility must be tamed.
Among experts, a discussion about planning-led approaches versus agile software development can quickly become charged with missionary zeal. This is hardly surprising because plan-based and agile models do seem to be worlds apart. On the one hand there are the plan-based models. These are based on the assumption that the specifications are essentially exhaustive and that adding requirements later on is something that should be avoided. On the other hand there are the agile models. These have a reputation for hurrying on ahead and completely neglecting many project standards, such as orderly documentation.
Your IT department, however, does not focus on ideology. It focuses on reality and results. It therefore makes sense to combine both approaches.