Final answer:
Kotter believes that change most often fails not because of poor planning but because of ineffective leadership.
Step-by-step explanation:
Kotter believes that change most often fails not because of poor planning but because of ineffective leadership. Communication is a critical aspect of effective leadership, but it is not the only factor. Effective leaders are able to communicate the need for change, inspire others to embrace it, and ensure that the change is executed effectively. Therefore, leadership is the correct answer.