There might be a good reason for this. Raster effects were already really good in newer games, and ray tracing could only improve on that high bar. It’s filling in details that are barely noticeable, but creap ever so slightly closer to photorealism.
Old games start from a low bar, so ray tracing has dramatic improvement.
Imo it has less to do with photorealism vs non-photorealism and more to do with pbr (physically based rendering) vs non-pbr. The former attempts to recreate photorealistic graphics by adding additional texture maps (typically metallic/smooth or specular/roughness) to allow for things ranging from glossiness and reflectivity, to refraction and sub-surface scattering. The result is that PBR materials tend to have little to no noticeable difference between PBR enabled renderers so long as they share the same maps.
Non-pbr renderers, however, tend to be more inaccurate and tend to have visual quirks or “signatures”. For an example, to me everything made in UE3 tends to have a weird plastic-y look to it, while metals in Skyrim tend to look like foam cosplay weapons. These games can significantly benefit from raytracing because it’d involve replacing the non-pbr renderer with a PBR renderer, resulting in a significant upgrade in visual quality by itself. Throw in raytracing and you get beautiful shadows, speculars, reflections, and so on in a game previously incapable of it.