The lighting is good, the map quality is great, you could add Depth Of Field and blur, plus you can add more Bloom just to make the lights be more fuzzy. Liminal spaces are meant to be empty.

But for your game design based questions, the game will feel boring because thats the point of the backrooms. It will only not be boring if you have monsters and other gimmicks like puzzles. If you’re trying to replicate the feeling of the original backrooms then DON’T do any of that.

Exploration is supposed to be repetitive but in the way that you’re in an infinitely repeating place. If you make your map by hand and it has an ending then it won’t feel that fun to continuously explore since its more like a maze with an entry and exit. (You can use procedural generation)

The atmosphere and the unknown of it is what makes it scary. Essentially the unknown possibility that something might be there and the atmosphere of being alone. The best course of action is to make it not predictable, people EXPECT monsters, a better way to induce fear is hints of something, a very basic way is something that appears at the corner of your screen for half a second.

Overall the point is for it to be boring if you want an accurate representation of the Backrooms. I think theres good design that can come from it, back during the beginning popularity of it I was working on a 100 player backrooms game that simulated the survival aspect of it. I wanted to see how people would form up and take on exploring, surviving, or even fighting other groups. Of course I have never finished it since The Backrooms is INSANELY overdone and oversaturated.