If you're making your own models, another option to somewhat sidestep textures is vertex colors.
At the very simplest objects can be 1* color, though it's still quite easy to color some details on low-poly models if you keep it in mind when you're designing your mesh (which going for an aesthetic, is the goal anyway).
Note that per-face VC is an option (in Blender: color attribute>domain:face corner, and then use selection plus the paint mask option right next to where you switched to vertex paint mode). You can also use the Spyro skybox trick to fake hard edges using your mesh.
Lots of simple options with big look changes too (unshaded vs. shaded, matte vs. plastic vs. metal, manually-painted VC shadows).
Adding even multi-use textures onto this, I'm not quite sure on especially as it requires messing at very least fixing the UV map+re-exporting. After that, object scale may be an issue (unless something like triplanar works for you).
I even tried doing my own watercolor stuff, a failed matcap texture (which might be a fault of the shader) and a maybe-fine splatter texture. It seems like going this route is a step up in one (if not multiple) skills to be an improvement rather than reduction over just VC. A generated noise normal map for metal (maybe glass/wood) is a somewhat more viable exception.
* even if you're using CSG (or say, textmesh) and not interested in VC, it might be a good idea to use a material that allows setting a color per-object via a shader parameter (this can be done via visual shader with ColorParameter plugged into albedo, blend mode can be used to allow grayscale texture like noise). A slight step up from graybox... unless your room is a cave, having color other than gray/white is an easy way to improve the representation enough for it to be playable.
EDIT: Alternatively, you could also just get the colors by using a set of materials like a color palette (stone, wood, grass, dirt, metal?).