Not really objective in real life. There is no abstract human in a vacuum, everyone has some previous knowledge and biases. If you ever had to train a grown up how to use a mouse and the ever illusive concept of double click, you know that even with some level of skeuomorphism there is a trouble at grasping new concepts, and if we go into more complicated territory, all bets are off. Maybe for a blank slate without any prior experience existing in society and operating tools, there are some high level abstract concepts, but for a real person, intuitiveness basically means "looks familiar to a something that I personally have seen before"