Just a heads up, when folks say “complex 3d objects”, it’s usually assumed that they’re talking about things like GLTF files, which contain geometry, materials, lighting elements, animations, etc, and which Unity/Unreal can absolutely load/unload at runtime or even stream from a media server online (so they don’t have to be in the binary).

However, once you cross over into scripting code, you are in fact crossing a barrier, and it does become harder to hot-reload the way you can in a JS app. Like, the fact that Unity scripts are written in C# and have to be compiled and linked is a pretty huge impediment that you don’t face when loading almost any other kind of asset.

I’m right there with you: Hot-reloading and 3D is a thrilling combination, and tools like react-three-fiber are miles ahead of anything I’ve seen in Unity-land in terms of laying foundations for stuff like this. I’d recommend emphasizing “hot-reloading code” when drawing this distinction with Unity/Unreal folks to better get across the magnitude of what you’re looking for.