Well, you can only physically expand a single school so far, but I get what you mean. I think the bigger problem is this concept of “elite universities” and this sort of credential signaling that seems to matter so much. Honestly, I can’t tell how much it really does matter. I went to Valdosta State University (never heard of it? Nope, neither has anybody else), but have worked with Harvard and MIT grads who respected my opinion and treated me as an equal. My 15 year old son, who I’ve never really pushed too hard to worry about getting into a “good” college worries about it anyway, because everybody he knows is worrying about it. He says things like, “If I don’t do well on this test, I’m going to end up going to Texas Tech” and I think, “Hell, Texas Tech is better than where I went to college, and I’m doing fine… should I tell him not to worry so much or encourage him to shoot for the top-ranked colleges?”
In any case, I don't think you should have to graduate from a prestigious college to find work that helps you live a good life. Maybe this involves making a place like Harvard accept more students, or maybe it involves improving the quality and our perceptions of middle and lower-tier universities. I don't know.
If everybody wants to go to Harvard then why can't they expand the school and accept more students?
Because the same brand of metrics trolls who are screwing this up have also screwed up in the school rankings by making schools rank better if they reject more applicants, so now the schools optimize for that.