The electron apps I've seen don't really have much UI. As soon as you build an app with some complexity it will start being a problem.
As a native Mac developer I can drop in things like a predicate editor for defining filters or queries. They come with Cocoa. I can put in sophisticated table views and tree views. I can connect all of this easily to core data which loads from a database objects on demand without any code needed to be written by me.
You see this sort of shortcuts in the electron apps I've seen. They don't have proper GUI for preference configuration like any Mac app as they can't get that for free. Atom doesn't have a regular file open dialog. I use that a lot, dropping a file into it to jump to a particular location I got open in Finder (file manager).
My preferred editor, TextMate has very little development resources behind it compared to Atom, yet it has a far richer GUI. You got a GUI for creating and editing plugins. Not just editing config files. You got native rich UIs for selecting fonts and colors. You don't have to write font names and color names in some config file.
There is a certain irony in the claim about how stuff like Electron saves you cross platform code, when what is usually not cross platform is the GUI, and the electron apps I've seen has very little of it. Try making something with the complexity of Keynote, Pages or Numbers in electron and I think the lack of a comprehensive set of prefabricated GUI components will start making its mark.
Not to mention the numerous native APIs which exist which you have to duplicate, e.g. for vector graphics, animations, 3D graphics, audio, video, font handling, OpenCL.
How about people with disabilities or internationalization? You got great native tools for doing that, how do you accomplish that in Electron without re-inventing the wheel?