Doesn't work that way.

Every student probably wants to go to Harvard, demand is unlimited. If they lowered the standards for example, there would be more applicants.

The number of applicants varies by all sorts of factors. Students probably have started applying to far more schools than otherwise. There are more total uni students, even if the number of seats across america has grown commensurate, the number of applications to Harvard will still go up.

Finally, Harvard probably wouldn't be Harvard if it were 10x bigger, moreover, they have no obligation to do so. They can do as they please, there are tons of good schools in America.

This is not the issue we face with selectivity and race/class/gender, that's a lot harder and it's a problem they cannot avoid.