Not memory safety.
> Zig is also good at game development which Rust is not good at.
Let's see. Over just the past year in Bevy I've implemented GPU driven rendering, two-phase GPU occlusion culling, specular tints and maps, clustered decals, multi-draw, bindless textures, mixed lighting, bindless lightmaps, glXF support, skinned mesh batching, light probe clustering, visibility ranges with dithering, percentage-closer soft shadows, additive animation blending, generalized animation, animation masks, offset allocation, volumetric fog, the postprocessing infrastructure, chromatic aberration, SMAA, PBR anisotropy, skinned motion vectors, screen-space reflections, depth of field, clearcoat, filmic color grading, GPU frustum culling, alpha-to-coverage, percentage-closer filtering, animation graphs, and irradiance volumes. In addition to extremely rapid general engine progress, there have also successful titles, such as Tiny Glade.
Whether Rust can be a productive language for game development was an interesting question a few years ago. At this point the answer is fairly clear.