Answer: Objectivism holds that in a society in which people deal with each other by trade, there will exist a "pyramid of ability." It is a pyramid in the sense that those who provide the greatest values (including skill, technology, and capital) are at the top: They run businesses and organizations; they are the "movers and shakers." Those who contribute the least and benefit the most are at the bottom: They hold down jobs.
Note that the pyramid of ability cannot exist in a society dominated by government "pull"; then only the biggest manipulators, demagogues, and bullies end up at the top of the social order. In a society based on trade, by contrast, one rises to the top by one's ability to serve the interests of others and to provide others values like good jobs, new technologies, needed capital, and organizational skill.
The pyramid of ability recognizes the social contributions of the people that make great productive efforts possible. These investors and inventors provide the companies, technologies, and physical plants that raise the productivity of a person of even very modest knowledge or skill to towering heights. Think of how much an auto-factory worker makes in today's society; then compare that to what he would make if he tried to set up shop on his own. That's an example of how we benefit from participating in the division of labor, and from the ability of others to organize efficient means of production.
However, it is important to realize that one's place on the pyramid of ability does not represent one's basic moral worth. The pyramid reflects one's social worth and one's social position. One's moral worth is not unrelated, but it isn't equivalent. You have to be a "mover and shaker" to be of great of value to others. That goes without saying. Even a great artist or inventor who labors alone and unrecognized will be considered of great value by others when they find his work to be of great value.
But Objectivism advocates an ethic of rational self-interest. Your own happiness is your highest moral purpose. Your moral perfection consists in living well and achieving happiness. Your moral worth thus isn't based on what others think of you and isn't directly connected to anything you might do for others.
To live by rational self-interest while living in society, one needs to interact with others in ways that are appropriate to one's interests and skills. In other words, one needs to find the right level in the pyramid of ability. Here is what Ayn Rand had to say on finding the right level:
....to cheat your way to a job bigger than your mind can handle is to become a fear-corroded ape on borrowed motions and borrowed time, and to settle down into a job that requires less than your mind's full capacity is to cut your motor and sentence yourself to another kind of motion: decay.... (Atlas Shrugged, p. 1020)
Does the pyramid of ability mean that you are unworthy if you are a janitor? Plainly you aren't a productive titan, at least in that role, and you are paid accordingly. Your pay is a measure of the values others place on your work. The pyramid concerns the size of a person's contribution to society. But the standard of life success for any person derives from that person's own needs, capacities, and purposes.
Say there is a person of modest abilities, who has little education and who does the job well, and who likes taking care of the place. Then being a janitor is an achievement and good way to work for that person.
By contrast, imagine the janitor in question is both over-educated and over-medicated—he's keeping up his habit in his drug of choice and filling his off-work time evading the dreams he had in his youth and the skills he isn't using. Now that janitor is unworthy. He is unworthy by the standard of his own potential.
You don't have to be driving the motor of the world to be a worthy and successful person by the moral standard of Objectivism. But you shouldn't just be "along for the ride" either. Your life is serious business to you, and Objectivism holds that you should take an active hand in making the most of it. That doesn't mean you must be smarter, or better, or more successful than others in any given field. But it does mean that you should be able to look on your life with pride as a career of productive achievement, aimed at your values, by the standard of your abilities, and for the sake of your own life and happiness.