Stop it. We don't care about your personal experiences. They're anecdotal evidence. As a person who is pursuing a career based on science, you should just stop using those experiences as basis for anything.
Statistically, higher GPA/MCAT tend to predict better performance in med school, and better performance in med school tend to predict better performance as physicians.
Note the key word: Tend. Nobody has said that they're the be-all-end-all predictors for future success as physicians. YOU were the one who said, and I quote, "I think these stats provide no information about the quality of physician you can become." You suggested that those numbers were chosen simply because there has to be SOMETHING to narrow down the number of appplicants. Your statement seems to say that MCAT/GPA were chosen randomly, and we're simply suggesting that they do, in fact, predict future success as well as college experiences can predict(along with EC's, LOR's, and interviews).
As for the OP's question, it's different at different schools. Some schools don't read LORs before selecting people for interviews, some schools don't read the essays(heck, Vandy doesn't even send you a secondary until they offer you an interview), and some schools look at everything thoroughly. It depends on the school.