Shrug, I run Gnome apps in KDE all the time. They run smoothly for me. I’m sure the inverse is perfectly fine as well.
I certainly don’t expect most users to switch between desktop environments but there are so many of them that complaining about one is a waste of breath.
Qt apps under GNOME aren’t great thanks to the client side declaration drama with the GNOME team. In short, the GNOME team believes that programs should be responsible for drawing their own titlebars/chrome (as opposed to windows being provided standard chrome for “free”), and so Qt apps have to draw a simplistic makeshift titlebar which doesn’t match anything when running under GNOME.
I certainly don’t expect most users to switch between desktop environments but there are so many of them that complaining about one is a waste of breath.