Qt is a nice library, and was almost certainly the right choice for an open-source application like Wireshark that had previously used the execrable GTK lib on non-X11 platforms, but Qt tries really hard to make water not wet in MANY cases.
Just look at what it takes to get a Mac Qt application to work well in full-screen mode on multiple monitors. Or handling keyboard-focus changes when a notification window pops up (especially one for iMessages). Or any number of things where the underlying platform libs on Windows, MacOS, and X11 differ significantly.
People who've only programmed web applications don't understand how weird platform GUI libraries are or how many corner-cases they have, especially when dealing with multi-window applications, keyboard focus changes, and notification & tool windows. Programming an application to this stuff is tricky - wrapping it in a cross-platform lib is nearly impossible!
Qt exactly proves the point that cross-platform libraries will NEVER give you the same high-quality experience that native applications written to the platform libs will.
Three common ways of sucking, I find, about cross-platform apps is that they are often slower, more resource heavy and "a bad citizen" on the platform. Not all cross-platform apps falls under any one or all of those things, but many does, in my experience, and those that don't always suck in another way.
Do you feel the same way with QT?
There's a reason all of those you cited failed. That reason is not "a cross platform environment can not be good".