Each dinosaur was modern for its time.
And so was XAML. Time is passing and now it takes significant excavation effort to find out a project that uses it. Git-for-desktop used to be a XAML app, now it is an Electron app. And so on.
QML is a palliative or compromise if you wish: let's take existing widget-tree-based UI and add some declarativeness to it at least to compete somehow with the web tech stack flexibility and explosion of ideas. Desperate move I would say.
As an C++ UI developer and then UI architect I was working on one project that transitioned from pure desktop VB + native application to pure Web based app. So "I've been there, seen that" and many times since then, all pro et contra of all these.
At some point I've asked myself the question: "Ok, what would you add to Web UI stack so it will be really useful on desktop?"
So I took C++ again and made the Sciter. It is a modern engine that works as on modern high-res monitors and GPU hardware as on ancient XP machines. It supports as retained UI as immediate ones a la ImGUI. As C++, Go, Rust, Delphi as script. As Angular (data bound UI) and React UI (vDOM,JSX) approaches as classic direct element tree composition from native code.
Yes, all this is using HTML/CSS vocabulary because it is a) convenient and flexible, b) 90% of UI developers are Web developers these days and c) HTML/CSS are here now and for generations to come.