As you said, this is a short demo, so I'm not going to be critiquing overall polish of the game.

Let's start with the positives:
+ Graphics are not just good, they stand out and grab your attention (in the good way).
+ Ambience Music is good
+ It's always good to see Native American cultures and PoCs having central roles in video games.
+ The automated talking was a bold choice. It passively tells the audience, "hey, this character isn't you, you're just along for the ride." If I might make a suggestion with it though, you may make it so that non-spoken inner dialogue is broadcast in a way that doesn't interrupt the game's passage of time, and preferably over a translucent text box instead.
+ Atmosphere was by far the best aspect of this game. Your music, your graphics, your story, all of it worked well together to create a distinct tone.

Now let's get into the not-so-good.
- For a scientist, he sure is a chatty cathy. You may be better served by at times letting the atmosphere tell the story, rather than a soliloqy from the protagonist. Show, don't tell.
- Sound Effects and Animations are a bit too big and "animated" for a game with this tone. More subdued sound effects and animations will better serve you here.
- The ability the protagonist gains before the demo ends: It felt extremely clunky and immediately pulled me out of my immersion. If it doesn't fit into a big plan you've got down the line, remove it completely. If it does, rework it so that using it doesn't take so darn long.
- The combat was the weakest aspect of the game. It felt totally out of place. Turning the game into either a stealth game (hiding from enemies) or a straight exploration game (Enemies aren't going to kill you) may fit better.

Overall though, you've got a lot of potential here. I hope to see further updates on this in the future.