I hate to say it, but I have to disagree on this point. Apple did come up with a UX that takes noobs completely seriously. But it does so by leaving out the hackers.
In short, you simply can't make a universal UI. Every compromise made towards one group of users alienates the other group.
In this sense, Jolla is (in my opinion) hitting a sweet spot; they've got a very powerful open-source framework (Mer on top of Android using Hybris), and a very user-friendly closed-source interface (Sailfish) on top of it.
Open-sourcing Sailfish would be, I think, stupid...
However, I believe that a different UI should be built on top of Mer, a totally open-source UI that focusses instead on functionality and ease of access to features. You can't make a single universal mobile UI, but you can make two opposing UIs on top of a single universal mobile infrastructure. This, I think, is the optimal way forward...