Qt Quick/Declaritive/QML was Nokia's reaction to iOS and Android. They wanted an easy transition for JavaScript developers.
It's finally matured into a usable system now that application processor horsepower has caught up in the embedded field. It only took 12 years.
Also, there's nothing wrong with using Qt Quick from C++, or using QML without Qt Quick at all. what matters is your project, not what whatever best practices say.