Why is lack of development necessarily a problem? Lots of very useful programs have seen little development recently because they already do well what they are supposed to do. In the case of user interfaces, it is far from clear to me that development represents progress. Personally, as someone who makes heavy use of the command-line and has zero interest in copying MS Windows, I was quite happy with the window managers of a decade ago and currently have to spend time setting up a new machine to configure Gnome Classic the way I like it. Developments like Unity are just an impediment. I recognize that other users, and in particular, other types of users, have different preferences, but I see no reason to impose the type of interface that one class of user likes on everyone else.