"The use of metaphors worked when people didn't know what a computer was, and the only way to make its UI make sense was to mimic real-world objects. Now, this is no longer necessary. It's been 40 years."

I disagree strongly. It is now more needed than ever. 40 years ago, the majority of people using computers knew what they were doing. Now, they're everywhere, and people interact with them every day. It's very common to have to interact with a computer we have never interacted with before, and the need to give visual clues to the user is far more important than ever before. It's also very common now for people to simply reach out and grab new software; a well-designed interface that uses visual clues and cues to help people achieve their goals is much more important now than the days when people would actually sit down with the manual to work out how to operate their new piece of software.

I am routinely unable to immediately answer a phone that isn't mine because none of the pictures drawn on the screen are obviously about answering a phone.