The irrelevance of an institution starts as an internal process. Most of the time, it occurs as the result of sclerotic thinking. As a catholic, I can use the Catholic Church as a perfect example. The relevance of a religion is the liturgy. The rites and liturgical activity is the transcendence between the spiritual and physical worlds. When you restrict the priesthood to a small population, you deny the faithful of the mystery that allows you to soar to heights of understanding. These understandings give you perspectives that change your world. This change provides you with the ability to grow and to learn how to cope with the trials and joys of life.
Restrict the requirements for entering priesthood, and this decline decreases liturgical opportunities. A narrow population that is overworked struggles with survival rather than exploring spirituality within a changing world.
This same principle applies to all institutions. When governmental representatives are employees of special interest groups, rather than their constituents, it goes the way of the diminishing priesthood. Look inside, rather than seek explanations outside the institution.