I found it especially interesting that the author challenged the idea that the church's declining growth rate is mainly due to external factors by comparing against the Jehovah's Witnesses and the Seventh Day Adventists, both of which he found to have much more favorable growth trends than the LDS church in many parts of the world.
Abstract. The Church of Jesus Christ of Latter-day Saints faces diminished prospects for growth in the twenty-first century due to both institutional and societal factors. Growth rates in congregations and active membership averaged below one percent annually from 2009–2019.
Fertility, retention of member children, and new conversions have experienced ongoing declines. Institutional decisions that were once adaptive have become liabilities hindering growth and internationalization. The dichotomy between the Mormon “homeland” and the “mission field” has fueled asymmetric information, misaligned incentives, principal-agent problems, and a culture of nonparticipation in personal evangelism by leaders and members. Reforms have sent mixed messages without resolving underlying pathologies.
Societal conditions are decidedly less favorable for LDS growth than in the late twentieth century. The human rights situation has deteriorated worldwide, Christianity is experiencing proportional decline in most world regions, and prospects for mission outreach in unreached nations are dim.
Medium-term growth in active LDS membership and congregations is likely to average below one percent annually. Over longer periods, losses may occur. The faith experiences its brightest prospects in Africa, where it is likely to achieve active growth. The LDS Church has lost its competitive advantages and is likely to continue to underperform its major competitors.
Stewart, David G. 2022. “The End of Growth? Fading Prospects for Latter-day Saint Expansion,” Journal of the Mormon Social Science Association 1, no. 1: 21–71. https://doi.org/10.54587/JMSSA.0102
There is a substantial section devoted to the problems with the missionary program and how it has prioritized baptisms at the expense of real conversions, which I think will be familiar to anyone who has served a mission.
There is a strong implication that institutional and leadership failures have caused the church to make poor decisions with regards to its long-term growth, and that it may have already missed its chance to become a major world religion.
The paper's conclusions about the future of LDS church growth are quite pessimistic:
Trends point to continued underperformance of the Church of Jesus Christ of Latter-day Saints compared to its competitors. While a range of possibilities exist, the default path is for further decline of growth rates. The LDS Church is unlikely to regain its former growth trajectory. Prospects of becoming a major world faith have faded and are likely beyond reach.