I was looking at what they were doing, and they were not clicking on all the toolbar buttons. They clicked on correct button, except one of them that first clicked on the dropdown next to it, and then on the button. My point is that even non-technical users, without any prior knowledge of the GNOME design language, don't seem to actually find it difficult to figure this out.
You may have a uncommon idea of non-technical people. Such folks don’t know what a list view even is, and would have to have it explained. Not to mention a filesystem.
Yes—we can see it's a suboptimal design on its face.[1] Bunch of repetitive dots and lines, with misleading clues. Not everyone is going to respond to it the same way of course. Some folks don't bother with clues.
The main point is that this problem has been solved already, better and in the past, by products delivered to tens of millions of seats. Merely copying prior art would have sufficed.
Responding with, "I found some non-techies who didn't have a problem" is not a direct response to the idea that the design could be improved. Folks can persevere and ultimately succeed through poor designs... in fact we all do it every day.
Some of us would like to use products that are a little more thoughtful than the bare minimum attainable-through-perseverance functionality, however.
