I think it depends on your use case. Yes, a huge selling point Electron is being able to control the Chromium version. But, I can imagine a lot of less complicated apps don't need this.

Also, the Chromium renderer is only half of an Electron app. There is also a background thread running in node, which can pass messages to the renderer.

So, I can imagine that for apps that are more background thread heavy, swapping out node for rust could work quite well.