Durkheim says that religious is a binding force that promotes cohesion among people in a society. Because people share same beliefs and values, they show solidarity. Usually such sort of solidarity was depicted in primitive societies where all the people were equal. Durkheim termed such solidarity as 'Mechanical Solidarity'. Now, as the society progressed, it became increasingly complex. Today, 'division of labour' is the hallmark of industrial societies. People are no more similar, but different. Thus, division of labour promotes interdependence among the members in a society. Therefore, the earlier mechanical solidarity no more holds the ground. As people are different, they own different values and beliefs depicted in religious and cultural diversity. A number of factors ensue this diversity i.e., immigration, urbanization, etc. Thus mechanical solidarity today has been replaced by organic solidarity, according to Durkheim. That organic solidarity is based on mutual consensus and rules. Thus, in Pakistan that is an industrial and modern society, Durkheim's view of Functionalist Perspective of Religion no more holds ground because religion is no more a binding force.
Hope I have made you understood it !