How can I get shaders like these for my horror game? Tell me, please!
It’s worth having a look at Godot Shaders, a website with shaders under a number of open licences! Here’s a PS1 shader for Godot 4 - PS1/PSX Model - Godot Shaders
You’ll need to either design your own assets or find some low poly and low-colour 3D assets from Kenney or from Sketchfab.