Rust + OpenGL: Rendering 250,000 Dynamic 3D Entities at 50 FPS on a Single CPU Thread

I created an open-source game engine, Light Acorn, with a unique architecture designed for older PCs. The engine is based on Macroquad and Bevy ECS (there is also tobj for loading 3D models from blender) I asked for help with its implementation for old hardware. I've been solving the problem for 1 week (that's how long the article was under moderation). The result: 13,000+ Active 3D Entities at 60 FPS on an old 2013 laptop with 35% CPU usage.