My point is not about lack of usability or documentation. Rather that the nature of HTML+CSS+JS lets you do things you can't do as easily in either GTK or QT. In the latter, yes you can easily achieve a certain kind of UI, but not deviate from it, and even formatting/displaying a significant amount of information that doesn't fit into one of the classic widgets can be a bit of a pain.
That depends a lot on what you're used to. It takes me far less time to implement a custom widget that can format/display a significant amount of information that doesn't fit into one of the classic widgets than it takes me to fiddle with CSS to get it to center things correctly ¯\_(ツ)_/¯.
