Art: The cover photo is nice. Use of color's not bad, and everything is at least not distracting. Map is a bit too basic.
Writing: I like the central twist, that the supposed Death God is actually a protector that's going to punish the worshippers and then maybe everyone else if they accidentally came armed and committed any violence in trying to prevent the sacrifice. But there's no real story... no setup that justifies the players being here, or suggestion for wrapping things up. The premise is made a little unbelievable by the deadliness of the temple... the Temple of Peace has vats of acid to dissolve intruders, and a guardian that has no non-lethal weapons, just two massive death lasers? I guess it could make sense if the original religion was overtly hypocritical in a 1984-like "war is peace" way.
Game Design: I like the idea of just giving three adjectives for each area... that's an efficient way to nudge the Warden to come up with their own descriptions. I also like that the endgame can go different ways depending on when security is triggered and what the players have done. I'm not in love with the temple layout but I'm glad that you've made it nonlinear by adding secondary routes to the Ritual Chamber and e.g. that hole blasted in the wall of the Atrium, giving players some meaningful navigational choices instead of just funneling them from entrance to hallway to atrium to ritual chamber. Aside from that, there's a lot that I'm not crazy about, that feels kind of thrown-together and maybe more appropriate to a different system than Mothership.
Theme: I think the idea of an ancient mythology and then a modern one that gets it exactly backwards has merit, but could have been explored in a more nuanced and gradually-unfolding way than just some cultists accidentally triggering a guardian mech and getting themselves killed.
Layout: Everything is in a place that's usable and makes sense. Putting everything in boxes isn't the most interesting or visually appealing solution, but it's not terrible and keeps things from becoming a mess.
Utility: You've left it up to the Warden to figure out a setup that gets the players into the temple and makes everything make sense, but from the temple exterior to the mech battle, I can't see having too much trouble running this.
Favorability: As I said a couple of times, I like the central idea of modern cultists misunderstanding an ancient myth and getting burned by it. Everything else is not really my thing, as someone big on interesting characters, player-driven plots, and a more low-key, believable game world.