C++ is arguably one of the most complex popular programming languages out there. With Qt you get a lot of conveniences and built-in magic, but I'd say at that point it's not really regular C++. A good comparison could be writing plain Ruby vs writing a Rails app.

I'll admit my experiences with Qt have been fairly limited relative to my web work, but picking up QtWidget seemed like it had a much higher barrier of entry than a web tech stack. Although I'll also recognize that QtQuick and QML greatly seemed to streamline the whole thing, especially for getting started. Based on my experiences performance with QtQuick still left a bit to be desired, but it was still an improvement over most Electron equivalents.

It's also worth noting that these comments mostly apply for people going for a mostly-native look and feel. If you want to completely customize the look and feel of widgets, as many modern apps have recently begun to do, I think it might be easier to get started doing that with the web stack. Then again, I recognize that this just might be my inexperience talking.

It also depends on the kind of app you're trying to build. I've written lots of personal apps using server-side rendering and a tiny bit of JS and I love how easily I can deploy and access it from all devices. That's a kind of versatility you just don't get with native.

IMO, most web developers could probably learn a lot from giving Qt and other native toolkits a try.