You are missing the entire point of bringing in a consultant: plausable deniability and double dipping. For one, if you come up with some idea and it goes south

You are missing the entire point of bringing in a consultant: plausable deniability and double dipping. For one, if you come up with some idea and it goes south, guess who gets the blame. If you, on the other hand, come up with the idea to bring in McKinsey, and listen to what they have to say, and that idea goes south, you get a pat on the back for bringing in a great consultancy into the mix, and if things went wrong its not even McKinsey's fault but dubious things like "market conditions" or whatever they cite. The things they often recommend to you are sometimes bordering on corporate espionage made legal by proxy, taking what worked with another competing client in your field and applying that formula to your own work. Then of course these consultancies are for profit companies, creating another investment angle for anything that you do for shareholders that are invested in both your company and the consultancy. They are never going away. It doesn't even matter what they put in those slides and they won't be going away.