Art: I take it that you ran out of time before finishing all the NPC portraits, but what you have is nice.
Writing: Funny and effective. I like the casual tone. You did a good job of sketching out a memorable cast of NPCs with a minimum number of words. The tone is wildly different from most Mothership fare, which wouldn't ordinarily bother me much, but it's a little odd envisioning it as existing in the same campaign as some of the other Barrow stuff.
Game Design: My main complaint about this is that it's heavily railroaded. The party is going to the bottom of this thing and back out again just because it's there, there are certain steps that have to happen along the way, and the cast of NPCs and prodding from monsters are all sort of conspiring to make sure the players do all those things. Granted, you did suggest that there might be other ways to convince the pyramid to open the doors, but it's still structurally on rails pretty much the whole way.
Theme: It's definitely ancient mythology. It feels to me like it wants to use a different system than Mothership, though. The mechanics of Mothership are going to fight with the kind of vibe you're looking for with e.g. those monster powers, etc.
Layout: I think the map itself is really nice but it's a shame the way the text is just plastered over it without e.g. little label boxes or something. The direct overlaying of the text and the map's lines them both harder to see clearly, and gives a messy impression.
Utility: Full marks. Everything necessary is present for someone to run the scenario as it's intended, assuming the players are going to cooperate when herded.
Favorability: It's fun to read, but I wouldn't run it because a linear progression of encounters without much player agency is a personal deal-breaker. Again, just personal preference because that's what this category is for.