Qt is a particularly poor experience on macOS. Also the past few years all the new stuff in Qt was QtQuick, which seems basically like JS, and if you're into JS, why not just use Electron?

GTK is a non-starter for something professional, at least if the experiences of the GIMP and Inkscape on macOS are representative. (Also, it's C, which does avoid some ABI problems, but it's hardly suited for an object-oriented environment)

False dichotomy—in our case we’d rather _start_ on macOS and then build other platforms separately… than use Qt.