> GNOME uses gjs

I don't think gjs is a webview. It uses JavaScript, granted, but binds to a native toolkit, not to DOM and CSS.

They’re still fairly uncommon in macOS, mostly being used in places related to cloud service settings. SwiftUI and Catalyst (iOS bridge) are both much more common than webviews, and AppKit remains ubiquitous.

Meanwhile on Windows major features like the Start menu are written in React.

Worth noting that WebKit webviews also tend to be more lightweight than their Chromium brethren.