For desktop apps UI quality and rendering speed is paramount. There's a lot of stuff buried inside Chrome that makes graphics fast, for example, deep integration with every operating systems compositing engine, hardware accelerated video playback that is integrated with the rendering engine, optimized font rendering... a lot of stuff.
If your Rust UI library is as advanced and well optimized as Blink, then yes, maybe. But that's pretty unlikely given the amount of work that goes into the Chrome graphics stack. You absolutely can beat Chrome in theory, by avoiding the overhead of the sandbox and using hardware features that the web doesn't expose. But if you just implement a regular ordinary UI toolkit with Rust, it's not necessarily going to be faster from the end user's perspective (they rarely care about things like disk space unless they're on a Windows roaming account and Electron installed itself there).