Hear, hear! The desktop computer (and the metephor of "desktop") works. People have learned and adapted to be very productive with it.
I do not want a desktop computer with "the simple interfaces of mobile devices". I don't want to remember three-finger gestures on a trackpad, and certainly don't need voice-activated commands (it's faster and more accurate to type).
Like you, I'd also argue against the statement that "we now use smartphones and tablets most of the time", or that "they are much easier to use". This completely depends on what the user is doing with the device.
For certain kinds of communication, application or media consumption, sure mobile devices are easier to use. They're not that great for long-form writing (email, articles, books, programs), or as a personal information management system (file system, database).
All that said, the designs in this project are beautiful, and there are some useful-looking interface ideas. I found this statement at the bottom:
"Neo was designed to inspire and provoke discussions about the future of productive computing."
It has definitely succeeded in this goal.