They tried to replace our Qt GUI at work in this space with a react based one, the new UI ran like utter shit comparatively, even after a lot of effort was spent on optimisation.
Also, most of the world don't use high end developer laptops. Most of the world is the developing world, where phone apps on low end Android phones reign supreme.
React is no innovation at all, some folks got a bit enthusiastic with Haskell reactive programming papers.
No way someone really used Delphi and claims that it is faster to build UI with HTML/CSS/JS stack.
Best time I ever had in a job was writing WPF applications in C# using ReactiveUI. Once we really understood the underlying model we were plugging stuff together so easily. It is a really good model, but I can't see how React is a good example of it.
Of course I had lots to complain about then, WPF had bugs, C# has a number of big problems, but it was, overall, very nice.
Compared to the web stack and Electron, native GUI APIs are complete shit. Both for the programmer, but also for the user.
Reactive UI (in the sense of React, Vue, ...), the greatest innovation in UI programming ever, was made popular by web-people.
Unless you write some ultra-high performance app like a Browser, a CAD app, a music production app, it doesn't make any sense to use native GUIs. Takes longer to program, the result is uglier and with less features. And for those ultra high performance apps you don't use the native UI toolkit anyway, you program your own widgets since the native ones are dog shit and slow.