While I fully agree with your issues, and have experienced them too, (although comparing v8 on Linux to v7 on Mac – I don't use 1Password on Windows), those are just UI/integration issues. I don't think they're because of electron, but rather because the remake of the UI is poor.
FWIW, my main gripe is having to unlock each vault separately, as opposed to a single unlock as used to be the case on Mac / iPhone.
That one part yes, but if you can build most of your application cross-platform and only do certain things with "native" solutions you might get better bang for the buck. Discord and VS Code comes to mind.
Rust is hardly a "desktop-native" language. I expect it will have to jump through all sorts of hoops to interface with the Obj-C underpinnings of MacOS desktop libraries.
Regardless, even if the backend were pure Obj-C, the point is still that now you have a UI stack and a backend stack, instead of a single desktop-native stack, and you have to manage their communications. But I guess the money they save by not managing desktop-specific codebases eventually adds up...
FWIW, my main gripe is having to unlock each vault separately, as opposed to a single unlock as used to be the case on Mac / iPhone.