This is a mistake common to most case interview candidates. They start with the McKinsey approach. This is a very, very bad idea. McKinsey cases are those were the interviewer leads the case. If you are only trained to do cases in this format, you will never learn how to lead a case. This is no small matter. The prompts and guides provided by a McKinsey interviewer play a significant role in helping you through the case and you will struggle without them. It is best to first learn to do cases where you are pointing out the areas or importance, and once you have developed this skill, thereafter shifting to the interviewer-led format.