For doing serious UX work, having direct manipulation of the GUI is paramount. Modeling human cognition without actually seeing the design while designing is makes hard to actually do the core of the work. Qt creator/designer for Qt desktop/widgets shines here.

Designing UIs in text is where most frameworks fail. It seems really bizarre that more techie devs still seem to believe they can design good UI blindfolded.

Imho, C++ not is a language using which user facing software should be built anymore, but Qt at least makes the compromise bearable, making memory management less of a burden.

The problem with Flutter and Dart is that it changes so often; a 1-year old codebase is probably always non-compilable on a newer Flutter version. Even the language evolves quickly; I did some app on Flutter one day, only to discover two years later that the language itself evolved to support nullable types, and the official way of migration was to "just create a new project from scratch and copy your files to this new project, fixing compilation errors", because the amount of small items to tweak was too high.

Another problem with Flutter is that the build system is arcane, nobody understands it, save for framework authors. It's being marketed as "you don't need to understand it, just push this button", until something breaks, and something always breaks from time to time.

One could argue that it's good that the ecosystem evolves to a better version; but the problem is that often this "better" is different for different people. If we're aligned in the same set of definitions then maybe it's a positive thing, but when the definitions diverge, a problem starts to be visible.

So I wouldn't say that using Qt/C++ is harder than Flutter/Dart. Maybe for one-off easy apps that are forgotten about a few months after creation. But for long-term programming and maintenance, Qt/C++ beats Flutter every day of the week.