As someone that does this every day across all industries and project types, I agree 100%, but proper/effective planning is not a panacea for project success.

As someone that does this every day across all industries and project types, I agree 100%, but proper/effective planning is not a panacea for project success. Identifying and managing Risk is as equally as important. As is Interface (the people to people / team kind) management and correct Quality Assurance. On top of all of that you need good Project Governance to handle change properly, with clear limits and bounds for changing durations of activities, budgets, scope and acceptable quality, defining responsibility and accountability, delegating authority, setting regular reporting requirements and cadence. Managing (non-trivial) Projects well is difficult, it takes hard work and careful thought. That is why we struggle. We revert to System 1 for all aspects of project management, not just planning.