A simple concept, you have things with recognisable names such as "start", "file", "edit" etc for menus and buttons and folk can guess what they do and see where to find them. Works well.
Now look at the efforts of today's GUI muppets who hide thing behind bizarre icons or simply remove them altogether and folk get pissed off. Where are settings, and why is a cog-thing where you would expect to see them? They are not gears after all. Or is it some sort of burger icon, or maybe some dots for no bloody good reason. Left hand or right? Looking at you Chrome, Android and Firefox.
Then we have Win8 where you have to somehow know to swipe from some obscure corner to find something, and by touching the touchpad by accident in some equally obscure way you get the metro stuff thrown in your face. Fine for kids and some geek folk who are happy just to slap things around until something happens, but have you tried to help or support an OAP with this shit?
Yes, I know about the Windows key and search, but again for a lot of computer users they don't know the names of stuff, but are able to recognise them in a familiar menu location.
Oh and the same dumb-ass approach is what made Gnome 3 a whole lot shittier than Gnome 2. The whole "we know better than our users and their 20 years of experience" ideology so lets bugger around for no good reason.