Specular lighting requires light direction, which isn't given. Is fakeable. It also requires the normals of the 3D model, embossable from depth. But those normals ignore smoothing groups, which leads to this polygonal look:
Also, further detail like from the normal maps (which are usually combined with the face normals in gbuffer) is missing. This could be faked somewhat but still not very well.
Last but not least, it's common practice to have some sort of spec map, which is a texture that tells the shader how shiny a surface is supposed to be. Without such data (not retrievable/fakeable on ReShade in any way), a model will have the same amount of shinyness everywhere. Which means the filter will give skin, metal, cloth the same amount of glossyness.