I think a LOT of kids who apply are “average” excellent students, as I freely admit my D is. She is delighted with the college she has ended up at, and of course, she is only average compared to some of the truly amazing candidiates that get into those tippy top schools. By March 31, she knew with certainty that she would not get into the Ivy she applied to. She loved the school, debated endlessly about applying, and did put a lot of effort into the app. But she learned more and more about admissions at the tippy tops. Unless her essays wowed them, she wouldn’t get in, because frankly, what she offered wasn’t exceptional. And her essays didn’t wow them:-) She is a white female (obv), from an over represented state, and had nothing exceptional on her app. They could fill many classes with kids like my D. She looks at the kids from our school who are going to Harvard, Brown, Columbia, MIT and others, and they either have a hook or something exceptional, except one guy. He kept his acceptance quiet, and honestly all the kids are really wondering what he had that got him accepted.
To answer the original question, I reckon that many applicants are qualified just from grades and test scores. I do think there are plenty of kids who are just throwing out apps, hoping one will stick. I also think there are probably more kids that are great students who hope against hope that they might be one of the lucky ones like the guy I just mentioned.