Unity is just an example. And depending on the game you may actually be doing heavy work in "just the scripting language" instead of the engine. XNA, MonoGame, Love2D, etc. are all frameworks rather than game engines so they're absolutely doing typical engine work in the scripting language, if you need a different example.

> You're also ignoring the overhead of WASM -> WebGPU -> native graphics API

Wine -> DXVK -> native graphics API works great for many people. I can't imagine it having significantly worse performance characteristics, especially when WebGPU is closer to the native graphics API than DirectX on Linux is.

> not to mention how much harder it is to develop and debug that platform than it is a native one.

But why? You still have access to a debugger.