In Canada .5 dropout, in the US 3 1/2%, in the UK 5%. In Canada there are very few spots so the effort to get in and have a way to pay for the education happens before. Once you are in the pressure to remain is extremely high. But 11% still seriously think about quitting.
The decisions and effort need to be put in early in life. Very few go to college and decide to become a doctor. They usually have gone to college to become a doctor and select schools/programs based on that. For some it starts earlier than highschool.
When you finally become a doctor after the lifetime of work the job may not be exactly what was envisioned but it is too late.
Offtopic somewhat: I know of smart people who decided to started programming, drawing/painting, inventing, writing, practicing law after age 35 and are enjoying careers. I know of no doctor ever.. is medicine that difficult for someone past 30?
Undergraduate medical education in Europe is commonly five or six years so yes, it could really be streamlined. If summers weren’t taken off you could fit medical school into four years. “Weed our and tire out” makes it sound like there are people who drop out of medical school when it barely happens at all.