This sounds rather dismissive. The company (and others like it) has been around for decades. Most of Fortune 500 has leaned on their advice multiple times, and their advice doesn't come cheap. So your implication is that these companies are being scammed into repeatedly wasting their money and are apparently not smart enough to figure this out. To me, that feels hard to believe.
It's conceivable McK and other actually do offer some value. A 26 year-old may not have tons of real world experience, but working at McK would allow him/her to have exposure to a global team that has worked across many companies in the industry. Having an understanding of best practices across multiple companies in the industry is valuable. It's also valuable to come in with a fresh perspective that is not heavily influenced by working at the same company for decades.
It's conceivable McK and other actually do offer some value. A 26 year-old may not have tons of real world experience, but working at McK would allow him/her to have exposure to a global team that has worked across many companies in the industry. Having an understanding of best practices across multiple companies in the industry is valuable. It's also valuable to come in with a fresh perspective that is not heavily influenced by working at the same company for decades.