I highly doubt that the optimal GUI development is at “modern reactive comp frameworks”, when decade old desktop frameworks had better tooling than that.
I seriously doubt that. Mobile platforms and web would be moving towards "decade old desktop frameworks" if those were superior.
Mobile platforms are most definitely not web technology, they are much closer to desktop frameworks. And the only reason the web is not doing so is (was) due to backwards compatibility and HTML being a bad target. But with WASM and canvas-based renderers, desktop frameworks sort of make an appearance on the web (though I personally dislike the canvas-oriented design, which basically throws away every accessibility)
It's like when people whinge about Electron. Electron gets you a runtime that's near identical across the major platforms, with a11y (something the Linux native toolkits still don't have their shit together on) essentially for free, plus you can use modern reactive component frameworks like React and Vue on the desktop. Yeah, I'll pay 300 MiB for that.