Haven't used Qt for a few years, but back then QML, QtQuick, etc have been optional features. You absolutely could write all your Qt logic in C++ only, in a somewhat similar way like the code shown in the iced READMEs. It is the same in any other classic GUI toolkit such as GTK+.

Biggest drawback in qt/c++ used to be the MOC. I guess they still have not gone rid of it, haven't they?