McGuire names four “narratives” that dominate the sociology of religion and that paint a fundamentally different picture of religion’s place in the modern world. These are: secularization, reorganization, individualization, and supply-side market analysis. She is careful to purposely call these narratives because, while each theory is based in evidence and data, data does not have meaning until a person derives meaning from it. Each narrative is a different interpretation of the same observations about the apparent decline of religious attendance in modern society.
Secularization posits that as the separation between church and state widened, subscribing to religion became something that was no longer “mandated,” but was rather a choice, and this led to more and more people choosing to be secular. Reorganization posits that there has not been a steep decline in religiosity, but rather, people are are reorganizing into smaller, more private places of worship. Individualization posits that the shift in religious attendance is due to more people treating religion as a more individual affair rather than a communal one, and are opting to practice religion in ways tailored to their individual lifestyles. The supply-side market analysis views religion like a business and posits that changes in religiosity are normal fluctuations.
In my opinion, I think that each perspective has valid points. I think some of them could even build upon each other. But, if I had to choose one, individualization would probably be my favorite theory. This is only because I feel like I have personally witnessed this theory in action. From personal experience, I feel like more people are treating religion as an individual experience and favoring interpretations of religion that benefit them.

-Posting this late because I realized I had typed up my response, but it somehow stayed sitting in my drafts and was never actually posted.