With the popularity of things like React, you now have a powerful way to express how the UI looks in every state, not just the initial one.
Step 1: People realise that Electron apps look different and do not fit the OS.
Step 2: Big company invests and creates a library that supports Win/OSX looks.
Step 3: Same big company creates a RAD type tooling for it.
We present you a revolution - Big Corp. RAD Tooling 2020 a la Borland Delphi 2007.
This is not an issue for most people. I like to use Spotify (the desktop app) as an example - it's a pretty good looking app, works nicely, and yet it uses an HTML-based UI.
Microsoft's own UWP also looks vastly different than native Win32-based apps.
The resource usage and slowness of Electron apps is a problem, but that is caused by using the entire browser runtime. When it comes to the capabilities of a UI framework, one of the questions I ask is "Could you build something like Spotify's UI with this? How difficult would it be?".
I guess the question boils down to whether a single tab in a browser which is properly managed by OS can compete with a good old native desktop app.
So far the facebook stack and react-desktop seems to be the best candidate for that description, but I don't neceserily think people would focus on getting it to the desktop styling. Universal Material UI (or similar?) probably would overtake that approach.