Earlier quoted context omitted.
Why not? The relationship between colleges and the accomplishments of the people attending them is tenuous at best. There are thousands of people at good universities that do essentially nothing, and wherever you are you have the opportunity to do better than them.
No, not really. People that get into Stanford or MIT did cool stuff when they were younger to get there. I still haven't done cool stuff!
More broadly, from an economic perspective, there are outliers, but most people only move one income quintile up or down from where their parents are (or don't move at all). So while we have some leverage over our futures, this suggests that we have less leverage than we believe. (So, for example, does the fact that 65% of millennials think they'll be millionaires by age 45, even though only 6% of Americans are millionaires.)
Certainly there's no reason to beat yourself up for not achieving things that are exceptional on an absolute scale (unless maybe you were born at the top and blew all your advantages).