The Project Manager is not an executive level role. They are not decision-makers. They are not even influencers. In many cases, they have little experience or formal training in project management and having a PMP certification doesn’t mean the PM is qualified to manage a large project. And yet, they frequently are blamed for projects that exceed the budget or fail to deliver the expected outcomes.
It is the responsibility of the PM to plan and implement the decisions that are made by the decision-makers. This leads me to the source of the problem. IT and business executive management have abdicated their responsibility for success. They direct the PM to implement what the business stakeholders request. The business stakeholders are not experts in technology or systems design. They know the outcome they want but they can’t provide the functional design and the PM only has authority to deliver what business stakeholders ask for.
IT and business executive management have to take ownership for achieving the desired outcome and to ensure the PM and the project team have the required support, budget, knowledge, etc. The PM and the project team will be pulled in many directions by conflicting requirements. Executive management must be active participants and facilitators to keep the project focussed on delivering the approved outcomes.