Why's that? VSCode actually looks to me like a native app. It's really fast and behaves properly like any native app would. I guess most people wouldn't notice it's not native.
I think gregman1 means bad from a resource consumption point of view. It takes a lot of memory and CPU compared to similar, non-electron based text editors.
VS Code is not 'a very bad app'. If you know of a comparable app that uses fewer resources to a significant degree please let us all know and I'm sure we'll all switch.