Max Weber argued that bureaucracy, and the increasing rationalization of human society, could reduce human agency and autonomy because it would reduce people to beings little parts in a machine. Bureaucratized society would be so bound by rules and regulations that people would no longer have the autonomy to act as they wished.
Weber identified a number of characteristics of bureaucracy. Among those characteristics were the fact that officials are selected based on competence, that they are given a set of written rules, and that they are to carry out those rules in an impartial way. In essence, these bureaucrats are being made into parts of a machine. They are not selected for their wisdom or discernment. Instead, it is their ability to competently carry out set rules that is valued. In a sense, they could just be machines because they are not being asked to exercise independent thought.
When all of society is organized around these ideas, people lose much of their autonomy and agency. Their entire life is carried out according to the rules of bureaucratic agencies. They become parts of machines because they are encouraged to follow rules in an impersonal way rather than using their judgement and humanity to decide what to do.