Is Joseph Smith realized as puer aeternus? Somewhat like Jesus, who is portrayed as Christ-child, Smith is manifested as puer aeternus when situated within the church context. Smith as farm boy reinforces maternal and interfamilial tenderness, combined with a love of the Heavenly Family - "This is Joseph Smith Snr.'s son, hear him."
By projecting the image of puer aeternus upon Smith, he is metaphorically castrated and thus asexual, although with Emma, he plays the role of Bo and Peep within Heaven's Gates. She is more playmate than equal partner. This sidesteps the issue of sexual controversy.
This contrasts with the avuncular and grandfatherly style of the First Presidency, who rely on the young spawning of Mormons (by twenty somethings) in order to strengthen intergenerational sentiment. The First Presiency thus acts as senex to the puer aeternus archetype.
Infantilism is a context of the nostalgic, and recursive nature of the late church and indeed late capitalism. By establishing lactating nostalgia, the church becomes mother proxy within the patriarchal structure, with Smith as substitute son/brother. Just as the secular world entraps kidults within fast food, Star Wars nostalgia, and Furry Fandom... So the church relies on primary songs, vows made at eight and the unobtainable bourne of youth to which we cannot return. The church produces asexual adults who are mired in adulthood, while the figure of Smith is not actualized and cut off in physical death before he reaches senex, and in representational death before he reaches true adulthood.
I think that all of these definitions apply to how the Church of Jesus Christ of Latter Day Saints views Joseph Smith. And I also think that the OP is making a very critical (if somewhat intellectual) criticism of that church.