You cannot use yourself as an argument about the productivity of Rust, you designed this language!
Joke aside, the velocity of the Bevy Engine as a whole is indeed a testament to Rust productivity.
Last year I had two groups of students who built a multiplayer FPS and a Tower defense respectively after just one and a half days of Rust class so the learning curve is clearly not as bad as people like to tell on HN.
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.