Back in the day, if you wanted to become a doctor, you just had to get the GPA, get an MCAT that isn't garbage, submit the app, and pretend to be a sociable individual in your interview. Boom, you're in. This is what your 50-something year old family doctor and neurosurgeon did. This is what you should have to go through, but it isn't because population boom.
Now you absolutely need extensive research, volunteering, LoRs that talk you up beyond your ability, unnecessary shadowing hours, ECs that make you stand out, and even all that isn't enough. Meeting this kind of criteria is clearly set up for privileged individuals, who old doctors of today were lucky as hell to have avoided going through.
Your premise is incorrect. First of all, the percentage of applicants who are accepted to med school today has not changed in the past 40 years. Back then the acceptance rate ranged between 40 to 50 percent, with some year to year variation. That is still the case. You can look up the exact numbers if you wish. Most years, they were in the low 40's, exactly as they are now.
Forty years ago, the minimum competitive GPAs and MCAT scores were exactly what they are today: 3.5 and at least 80th percentile on the MCAT.
Forty years ago, you were expected to volunteer and shadow, and if you didn't, it hurt you chances of acceptance. Perhaps those activities were not done as much as they are today, but I have no way to quantify the difference, if any.
Back then, you certainly needed great LORs, and the interview process was just as rigorous as it is today, although there were no MMI interviews at that time. Extracurricular activities were valued just as much then as they are now. Med school classes always had their share of PhDs, athletes, and musicians. As far as I can tell, nothing has really changed in terms of the admissions process.
What has changed is that residency spots have become somewhat more competitive, and the USMLE scores seem to be more important. However, I can tell you that derm residencies were competitive back then, and so were plastic surgery residencies ( per what older specialists have told me ). It might be the case that some of the surgery specialties were less competitive then, but otherwise, things are really no different now.
I can also tell you that the really good applicants stand out, both on paper and in person, and get into med school without breaking a sweat. The process is very straightforward if you have the proper qualifications.
If older doctors are telling you otherwise, it's because they don't remember all the details of what they went through, or because they were particularly well qualified applicants, or most likely, due to "survivor bias" ( i.e. you are only talking to people who are doctors, so therefore, by definition they all got in. If you talked to people who applied to med school 40 years ago and were rejected, you would hear how hard it was to get in back then.)