Some cultures very highly prize medicine as a career. Members of these cultures are over-represented among applicants...
I'll reply at the end of this but I want to address that comment above first because I believe it needs to be explained in-context to avoid confusion amongst those misinformed about said cultures.
I certainly hope you are not referring to brown folk with that generalization because that would include me and you, or anybody for that matter, would be very mistaken if you think that the over-represented demographic that you are referring to applies to medical school solely because of cultural influence or a true lack of understanding of the career itself.
My parents encouraged me NOT to go down this route because of the time and money involved and to settle down with my "business" degree, get an MBA, and continue working in finance; very far from medicine. If I had continued down that route I would have been equally or maybe even more successful and I don't think I would be seen as an outlier in my community because I did't go into medicine as I am not the only brown guy who was not "pushed" to go into medicine. I voluntarily changed careers and entered this path in my 30's because this is what I WANTED TO DO and it's a decision I made ALONE. I am now a fourth-year at St. George's University in Grenada and I did very well during interview season and am now just waiting for my match in IM. To be honest, the way I went down this route would make most people in my "culture" cringe that I did it as an older student, accumulating debt, and putting off marriage and starting a family till a much later time than some people within the culture would consider ideal but I did it anyway.
I wouldn't say that certain cultures "prize" medicine as some type of a status symbol of sorts. You would be more accurate in saying that those cultures value very high achievement with regards to academics. Medicine, IMO, can certainly be considered the peak of academic achievement by any person let alone a specific group of people. The profession in turn does reward those high-achievers with job satisfaction, career stability, flexibility, and handsome pay among other things. I don't believe that is a career outlook valued by just one culture however. If a certain group of kids, brown kids lets say, are good with math and science then I would automatically expect that medicine would be very high on their career prospects list hence the over-representation of the applicants you mention but I don't think it is fair to say that culture is the root cause for that as somebody still has to make the grades and pass the tests. I would also argue that some of those cultures that, as you say, "highly prize" medicine as a career also include cultures who are not over-represented or not even minorities at all. Hell, I know Nigerian parents that push medicine more than brown folk but I don't think you were referring to Nigerians. The over-representation of any group of people is, if anything, an academic influence, not a cultural one. If all the "over-represented" applicants were stupid, it would be rather pointless for their parents to "highly prize" medicine as a career right? So lets be clear, over-representation of these people in the application pool is primarily a product of high-achievement first, population second, and culture not as much as you think. Last time I checked, a brown guy needs a higher GPA and MCAT score than their white male counterpart to be competitive so I'm going to go out on a limb and just say the brown guy/girl has every right to and would want to put their application into that pool if they are bringing high stats to the table; or in this case, stats certainly exceeding those of the average applicant.
To answer the OP's question rather bluntly, decrease physician salaries by 30% across the board, have non-MD's continue to dictate even more physician responsibilities and quotas, increase insurance regulations and decrease reimbursement even more, give greater autonomy and responsibility to NP's, PA's and other mid-level providers, and you will see that medical school admission statistics will sink like a stalling 747 once the word hits the streets.
Medicine is lucrative on many levels; financial, personal, societal, professional, and certainly the humanistic rewards. That's what most people see and that's why you have such high demand and competition because the outlook is usually one-sided. Focus more on the realities of medicine and maybe you wouldn't have such high competition as some of the realities of the career might sway people to other areas of medicine or even other careers flat out. To be fair, how much would you expect a teenager or young adult to know about medicine before getting into it? My understanding is certainly very different today than when I was a young volunteer at 16.
Personally, if an 18-year-old comes up to me today and says "hey, I think I want to be a doctor too!" I would steer that kid to a 3+3 BS/PA state-school route and tell them to start making $120K at 24, save up a ton of that money over the next 8-10 years and then if they decide that being a PA isn't cutting it for them and they indeed want to pursue an MD or DO, to go ahead and apply at that point as you can now you can finance your medical education with cash on hand all while coming into the profession with a very clear perspective of medicine most of your classmates will not have. You will also now be able to say 100% why you want to become a doctor and not something else. And I would bet my own money that it wouldn't be for the money or prestige and you would have the best shot at truly being happy with the decision to practice medicine.
Certainly not conventional but then again neither is culture.
