Okay - here are my thoughts. Don't expect anything too enlightening.
1. Defining "success" in medicine based on the competitiveness of the residency (either specialty or program) is a flawed metric. I can see how someone might think this is a good way to measure success because "competitiveness" by definition implies value and demand greater than supply, but 90%+ of spots in the ACGME match are in "non-competitive" specialties (defined here as all specialties except derm, rad onc, and the surgical subspecialties) (source: charting outcomes). Obviously this doesn't say anything about competitive programs within non-competitive specialties, but that's harder for my to quantify quickly so I won't attempt to because math is hard. Also, that's not to say anything about the osteopathic AOA match, which has many more spots, nearly all of which are in the "non-competitive" specialties. So if we're defining "success" as matching into a competitive residency (let's just for the sake of argument say specialty and not program right now), then <10% of medical students find "success". Obviously that isn't true.
2. A better way to operationalize success is to define it as going into the specialty of your choice, at the type of program of your choice, in the location of your choice, and ending up in the practice environment of your choice. The downside to this, of course, is that its essentially impossible to measure. But that's really the point. What defines success is individual to each person - not to the commonly espoused SDN mantra of ortho/derm or bust. Most applicants don't want ortho, or derm, or CT, or neurosurg, or whatever. I personally would flip my s*** if I had to do derm for the rest of my life. Anyway, we need to realize that our definition of success in this thread is not the definition of success that matters to anyone.
3. Most people at schools that would be most conducive to jumping ship to business/consulting/non-medicine/whatever will end up in medicine. Overwhelmingly so. If someone brings up that extremely misleading article about only 60% of students at Stanford going onto residency in 4 years and uses it as evidence I will have a spontaneous subarachnoid hemorrhage so please don't. Yeah, it sucks that some people end up outside the medical field, but ultimately, in my opinion, it's their education, and they can do what they want with it - and some of them end up doing great things with it anyway, even if it isn't practicing medicine.
4. Yes, sometimes the disingenuous but highly driven and intelligent person will be picked over the genuine but slightly less whatever person, but it is my experience (trigger warning: anecdotal evidence) that most people entering medicine do so with good intentions.
Anyway, those are my thoughts. They aren't eloquent, universally applicable, or necessarily even logically sound, but you asked and so I did my best.