One answer to this is the idea of a "positive-sum society." In such a society, resources are increasing rather than limited. This means that everyone can increase in wealth; an increase by one person does not mean a decrease by another. Even if one person is tying up wealth, others can still improve their condition.
Escaping the grip of powerful people is more difficult to answer. If the population is expanding (into the solar system, or to other stars), there will probably always be a colony to which one could flee. But probably the best defense against despotism is a good, stable government which prevents dictators from forming. Such a government has never been known to last more than a few centuries, but it may be very needed in the future.