A shader just carries the physical property of a surface and how it behaves in the world and “sometimes”doesn’t need a color texture like glass , metals plastic etc but for a shader to be realistic , specially at close range it needs all those other textures , roughness, diffuse, normal,specular and so on .
Textures are just as important and a good artist can make a model photorealistic by creating the appropriate maps.
You should probably take a shading and texturing class to become an advanced 3D artist and build a good portfolio.Finally as an example, a wood plank or a brick wall definitely need a texture map and UVs , a shader alone would not work obviously.
