Qt is still pretty good, but it's dated in comparison to newer frameworks like Flutter and React Native. No hot reloading of changes, manual widget management vs. React where you just re-define the whole UI every frame and it handles changes magically, no single source of truth for state, etc.
That's false, see QML hot reload[1].
[1] https://www.qt.io/blog/speed-up-qt-development-with-qml-hot-...
That's a third party paid addon. Hardly a fair comparison.