Isn't JUCE music-app only (or, mostly)? Also, I am having a hard time figuring out whether you are mentioning Qt and JUCE in a positive light, or a negative one...
JUCE is mostly for music, but otherwise fully flexible UI-wise and with tons of helper stuff for all kinds of things.
And the parent is obviously implying QT/JUCE are much harder to create a GUI than js/html/css/etc.
Have you ever tried to build a UI with Qt or JUCE?