Even if that’s true, the stock GNOME apps and third party GTK3/4 apps (which tend to follow GNOME design philosophy) work more smoothly under GNOME than those built with Qt or other frameworks, and so deviating makes for a materially worse experience.
And yes you can switch between multiple installed DEs and I have done so in the past, but that makes for a messy experience with many redundant apps that the user must clean up themselves. It’s a lot nicer to have just one installed.
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.
And yes you can switch between multiple installed DEs and I have done so in the past, but that makes for a messy experience with many redundant apps that the user must clean up themselves. It’s a lot nicer to have just one installed.