Well, I was just demonstrating how popular metaverses like Decentraland are built. These are built in the browser and leverage WebGL instead of using Unity etc. I agree with you that this is not suited for big games which should probably rather use Unreal or Unity. However, this tutorial is about how to build it for the web with the tools that the web and its ecosystem has to offer and is targeted towards web developers rather than game developers.

The advanced character is just called advanced character because the underlying GLTF model that I found in the web was named that way from the beginning. I didn't bother renaming the models and just used their initial names. So the naming doesn't refer to how "advanced" the component logic is. What do you mean with performance?