I've had in depth conversations with people on both sides of the fence and really dug down and made them explore and explain the why for either side.

What I found is that it boils down to whether or not you are fine with doing some initial setup. People who love KDE almost never use the OOTB configuration it is pretty much guaranteed that they have every intention of customizing the interface whether that's through themes changes in layout or add-ons that bring entirely different workflows. Almost every instance of a KDE desktop is unique when you dig into it.

People who love gnome do not want to configure anything ever, they are happy with the workflow as it is out of the box and thus happy with the environment. At the end of the day you can make KDE look and behave almost exactly like gnome, but if gnome already fits your desired work flow why bother? When you get the people that use gnome but do have complaints it's usually that there's only like one or two things they wish they could change slightly so it's not worth going to KDE and configuring everything to be how they want.

I fit into the first camp, i love KDE specifically because I can change virtually any piece of it to be exactly how I want. I do not use the out of the box configuration, I make a number of changes they are not major ones I get rid of the floating taskbar because I think it looks stupid like my graphics driver is broken or something, i make changes to the layout of the file explorer I make some context menu changes here and there change the theme change some things about how the windows behave. overall i don't think you would immediately notice sitting down at my computer if you were used to kde you would just discover things that broke your muscle memory as you went.