Art: Well-illustrated and aside from the stat boxes, one of the more readable examples of typography I've seen this jam. Could use maybe a little more color or, if sticking to black and white, some larger swathes of black to create visual structure. That said, it is thoughtful even in its minimalism and avoids looking like a basic Word doc, which is usually the danger when people opt for black-on-white throughout. Wrapping the text around the headers was an effective choice although "REUBEN MOSS" is a bit too long for that and maybe could be just "REUBEN" there.
Writing: I get the strong impression that there was a time crunch. As someone who edits for a living, this looks to me like a talented writer who was rushing and didn't edit themselves. There are typos as others have mentioned, and some places where the information has some structure but others where it's a bit steam-of-consciousness. That said, I think there's an interesting story here and the style of writing is effective at establishing vibes. I think with some restructuring and careful editing it would end up a 5/5, but right now there are too many parts that read like preparatory notes, not a final draft.
Game Design: This is probably too ambitious for a trifold, mainly because the way the plot is designed, exploration of the facility is the central activity, but you envision five floors each with multiple locations. I do like the thought you gave to fleshing out the NPCs and potential plot arcs.
Theme: Full marks. Very mythology and very Mothership, and those two thematic axes are well-integrated throughout.
Layout: Mostly effective. I think some things could use a bit more padding and the sections of text that are in point form, like Joseph's story beats, should probably have bullets. As with the writing, I get the impression that you know how to do layout, but were probably operating under deadline panic, because there are some things that are done well and other things that aren't done at all. Finally, I know that people read pamphlets in different orders, but personally I go cover, flap, spread, back, so when the introductory overview is on the back, I end up confused and trying to piece things together as I go. I think the inner flap or left panel of the spread are the safest places for that stuff, because you're physically compelled to see them before fully opening and getting to the spread.
Utility: I have to give low marks here because of the combination of unfinished aspects and too sprawling a concept to fit effectively into a trifold. Unless the Warden is extremely good at environmental ad-libbing, you're asking them to sketch five level plans for themselves among other prep.
Favorability: Full marks here. I think it's thematically great and I appreciate ambition even if it didn't really come to fruition under space and deadline constraints.