I located the original text to get more insight to the sentence. Basically it means that because there are so many people in one place and people are more connected, your unique skills are no longer (to be perceived) so unique. There are several others in the community who are able to do what you do equally well or better. You may have been the best shoemaker of Hicksville, Kentucky, but when you move to New York there'll be 20 others with equal or better skills.