Just because someone is a doctor, it doesn't mean they naturally had more capacity for intelligence than someone who didn't even go to school
The difference between say a doctor and someone without a college degree isn't a difference for capacity for learning or innate IQ.
First of all, people have different goals. So, not everyone is trying to become a doctor or go to college. But let's assume that was the case. Even then, factors such as opportunity for education, availability of support as a student, life choices, and general work ethic determine where people end up in life.
I am not saying that natural intelligence doesn't vary among people. All I am saying is that it's possible for a very intelligent person not to make it far in academics while someone with less natural intelligence can make it far in academics.
Overall, so many factors determine success in life. I just hate when people assume someone being a doctor and automatically conclude that they have above average intelligence and that's why they've become a doctor. That's extremely dismissive of the insane amount of of work ethic it takes to become a doctor. I do believe that you need at least an average level of intelligence to become a doctor, but the rest is about desire and hard work.
Note. People also confuse being informed/educated with natural intelligence. Knowledgeable isn't inherently more intelligent. But someone having more demonstrated knowledge than you is still a valid thing. So, I am not making this post to tell you to blindly argue with someone who is an expert at something than you are.