I’m having trouble understanding why the answer to this question would ever be “no”. The only exceptions I can imagine would be if a person is doing something physical, like a professional athlete or singer or dancer. A lot of people might not have the DNA to perform those jobs, no matter how much they worked out or practiced. And a very few jobs, like advanced theoretical physics, might require IQ points beyond the range of most people.
But other than that? Of course you could do my job, given enough training. I wasn’t born knowing actuarial science. I learned it, and (given a “good head on your shoulders”) you could too.