Major visual difference would be that whatever the editor font settings dictate, would apply to all the UX not just the text-editor tabs. But that, who would even mind.
The extensions compat would have to be NodeJS-based I guess, but the rest wouldn't have to be written in JS/TS I suppose..
Plenty of us are "happily Stockholmed" by the overall DX of VSCode but were there a Electron-less but otherwise 99+%-compat-and-keeping-up-with-vsc rendition (TUI or native GUI), we'd jump on it nonetheless.