Intuitive/easy to learn does not imply useful. Some times the most useful things are the ones that have a high learning curve. It seems the tech industry has decided that making things easy is more important than making them useful.
The point is that unless you are in a specific domain where complexity is an unavoidable necessity (let's take 3D modelling as an example for arguments sake) learning a UI, especially when it is a upgrade of a familiar product, should be a simple task of augmenting existing knowledge with a relatively small amount of discovery. I would argue the ribbon menu largely achieved this, Win8 in my opinion absolutely does not. So much so companies are preinstalling 3rd party addons just to get it to a state where people know how to achieve the simplest of goals.
Sometimes it is bad design. When you replace a perfectly good interface -- one users have grown accustomed to for decades -- and replace it with something different that offers no additional benefits, you're a bad designer.
