KDE is the best desktop experience available.
I agree that KDE still feels better though.
(I actually asked someone more knowledgable about this once and was told that it's my fault for using the file picker incorrectly and I simply need to stop doing that.)
The past 5 years though have been a nightmare, MS has really messed their UI up, and various applications/toolkits or whatever the problem no longer properly support the CUA guidelines which in the past were the one assured way of doing an operation cross applications and various OSs (windows+linux/kde).
Maybe its time to start going to a few developer conferences and giving talks about how useful system wide shortcuts that work across multiple OSs really are.
Control click seems to work.
Some other Gnome apps also work correctly so I think it's fixed in Gnome but not whatever GIMP is using.
That's a degradation from 2.10, or 2.16, from time even before the 3.0.
This, other UX and even performance (!) issues that have been mentioned in siblings as well as TFA makes the Gtk file pickers easily one of the TOP10 reasons to avoid Gtk and Gnome for anything.
The interaction design of these dialogs is simply shit. Windows (and also KDE, which has been using a copy of the Windows dialog for about 20 years) show how to do it correctly.