With any group of people, you always have a spectrum of talent and usefulness. I've worked with Stanford CS grads who would shock you with the inability to produce anything useful without handholding and worked with Stanford MBAs that I was surprised could even get their pants on in the morning. The problem is that the admissions process for most of these programs is less about the numbers and more about your ability to network or tell a compelling life story. If you can tell a story that impresses the admission folks, you're likely to get in. Sometimes this is reflective of actual talent, sometimes its a reflection of great story telling.
That being said, there a few incredibly talented and intelligent people in each class that will continue to allow these types of institutions hold the prestige that they do.