Olfactory sensibilty is an important part of perfumery. While it is not a prerequisite for a person to have a keen sense of smell (some skilled perfumers are unable to smell certain fragrance materials particularly musk and woody fragrances in their pure forms). One should be able to recognize the differences in fragrances.
One's sense of smell can change over time. It has been demonstrated that olfactory sensitivity declines as you age. There have been successful perfumers in the 60s to 70s age range. While high sensitivity is necessary, exceptional sensitivity is not, so, do not despair. Anyone can study perfume no matter the age.
One of the skills a perfumer should have is the ability to recognize slight differences in odor quality, this is able to be learned to some degree. Be mindful that there are differences between individuals to the extent to which this ability can be acquired, and the professional perfumer must be good at it.