While I agree with your point that social capital is a significant value offered by competitive colleges, I think that you miss the link between a quality of peers and quality of education.
In college, much of the learning happens outside the classroom. This means that if you are studying with classmates who genuinely value the education more and who have been working hard at learning through their high school years, you have a highly enriched learning experience. Both the classroom learning and the midnight philosophical explorations are more valuable. In contrast to peers at a less selective institution who may be more interested in drinking than learning. They won't push you to higher level thinking or higher quality work. The curriculum may look the same but who you experience is with greatly impacts the depth of education you receive.
While I agree with your point that social capital is a significant value offered by competitive colleges, I think that you miss the link between a quality of peers and quality of education.
In college, much of the learning happens outside the classroom. This means that if you are studying with classmates who genuinely value the education more and who have been working hard at learning through their high school years, you have a highly enriched learning experience. Both the classroom learning and the midnight philosophical explorations are more valuable. In contrast to peers at a less selective institution who may be more interested in drinking than learning. They won't push you to higher level thinking or higher quality work. The curriculum may look the same but who you experience is with greatly impacts the depth of education you receive.