"What responsibility do elite colleges have to provide opportunities for the large majority of Americans versus the 1%? "
The elites have never been all that much about this. But they are probably doing more today than they ever have.
When I was growing up first gen and lower middle class, I wasn’t thinking about attending an Ivy or even a state U that had dorms. I certainly wasn’t thinking about a private college that had things like frats, lacrosse teams and a golf course.
For me and my siblings it was CC, CUNY or a local commuter school. That’s still where mobility is most likely to happen.