Indeed, I consider that the cult of the dead, from what I have read and intuit, is one of the fundamental components of the human condition. You have done an archaeological and anthropological walk through this practice.
In my references there are many examples. It is emblematic that of Mexican culture, which is nourished by previous cultures (Nahuatl, Aztec). The book The Labyrinth of Solitude by the writer Octavio Paz (Nobel Prize for Literature) is very illustrative in this respect (I recommend it to everyone). Many of the funerals that Mexicans carry out exist in other towns and American countries, such as eating, drinking alcohol, dancing, telling stories, etc., around the tomb of the loved one. Before that, it was necessary to found their new habitat through the installation of the ceremonial center, which, according to Christian Duverger (quoted by me in my previous commentary), was based on the bones of the founding ancestors, which they carried with them.
Perhaps death, like birth, the extremes of life, is the great universal and eternal archetype.