I'll talk you through one of my first programs as an example; it was for an assignment in Object Oriented Design in Java, which was to make a very simple pinball game. There was some code given as a starting point, but it was terrible (it was essentially a C program shoehorned into compiling as Java, thus it didn't follow an Object Oriented Design and, whilst syntactically correct, wasn't really written in Java at all), though most (probably all) used it as a starting point. Being very new to programming, especially in such a verbose and overly-strict language as Java, I couldn't really follow the given code: I could see the API and get it to do the things I told it, but I couldn't understand all of what it was doing, and amongst those bits which I did understand I saw some obvious hacks. As a Physicist and perfectionist-who-never-ends-up-finishing-anything I didn't want to use incorrect code, and especially didn't want to rely on someone else's proof without understanding it (Curry-Howard and all that). Thus I did the first thing that anyone who's ever done any Maths would do and tried to work it out myself and see if my solution matched. The result was a program of which I was quite proud: rather than being a hack to shift graphics around the screen (as the provided code had been), I'd started from what I knew and had made a basic Physics simulation with graphical output (originally based on AWT then switched to Swing). The code was spread out amongst many classes, there were no hacks in the object system (although there were a few in the main method to set things up, but that was just for testing), it was very intuitive, was the largest programming project I'd tackled thus far (although now I'd consider it to be the size of a moderate experiment) and I had it running pretty early into the assignment. It now needed some recognisable objects from a pinball table (like flippers) and more game-like control. However, rather than writing these I just played around inside it. Constantly. It was fun to throw things around, generate hundreds of objects and watch them bounce around off each other but most of all it was fun to know that I'd made it. In the end it got marked as 70%, since all my playing stopped me from actually making any kind of pinball game (I talked through the code, but when running it just presented a bunch of balls bouncing off "pins" which were just fixed balls).
Now, what's this got to do with Gnome? Well, Gnome works really well. It's unobtrusive, stable, intuitive and does "what people want". Reading through Planet Gnome gives some design bugs (the keyring dialogue asking for a password without indicating what is after the keyring or why, allowing a trojan to ask for the keyring without the user having any indication that they're giving access to malware and not NetworkManager or Evolution or Empathy or whatever), a few posts on Zeitgeist, translations, some compatibility improvements and a call for more contributions to the 2.29 features list. Other than that it's musings about transport, architecture, low-level distro tweaking (nothing to do with Gnome, things like boot performance). It seems that there are three levels of Gnome developer (and I mean developer here as anybody involved in improving Gnome):
1) The it does "what I want" developers, who may maintain things but make very gradual changes (like layout changes, adding translations, etc.). To these, Gnome is an excellent platform which chugs away unobtrusively for them in the background and allows them to get on with life; their itches are the "papercut" annoyances that are small, but happen a lot (something like an info dialogue which doesn't have a "don't show this again" option).
2) The inspired developers who's itches are to push the platform in new directions. They work hard to do this, but as one-person-armies they can only do well on one thing at a time (for example UPnP support).
3) The ignored developers who's itches to make sweeping changes never really get scratched due to the inertia of userbase familiarity and developer apathy due to the adequate nature of the platform as-is. These include the Gnome mobile efforts, the online integration attempts and so on. For those wanting an example of inertia, take Nautilus's spatial mode. This is rejected in favour of the old one-window browser mode by many users, simply because it was there first.
Now, I am not trying to crap on the project, far from it I'm offering my observations of the development slowdown over the past 6 or 7 years I've been using Gnome and following its developers. I'm not in any way trying to undermine the efforts of those three groups I've mentioned, I am trying to point out the obstacles that each face and how they could be overcome.
Many of those developers in groups 2 and 3 could benefit from Gnome 3 stirring things up a bit to break the stagnation. The reason I put quotes around does "what I/people want" is because, in my opinion, there's no such thing. Recall Henry Ford's famous remark that if he'd given people what they wanted then he would've given them a faster horse. Nobody knows that they want something unless they try it for a while and integrate it into how they go about things. I'm frequently met with the does "what I want" argument with regards to Windows. If the current situation in Gnome is unfortunate then that lumbering beast known as Windows XP is the armageddon! Admittedly, Windows Vista is awful: those few of its features which are any good don't make up for the cost in performance, and many of the features deemed "good" by others aren't features they're just attempts at shifting responsibility for brokenness onto users (those damned popups!). However, since there was an explosion in computer ownership during the lifetime of XP (2001-2007), for many people XP is a fundamental fact about what a computer is, in the same way that a toaster is not a toaster without a spinny dial for toasting time. Of course there are those who lived through Windows 95, 98, ME (lol), 2000 and XP, and who saw Vista as the next rung on the steady upgrade ladder it was intended to be, but viewed it as not worth the wait compared to the more timely releases of the past, and no doubt the growing use of computers made its drawbacks all the more annoying.
The appearance of KDE 4 stirred things up in KDE land, but there was such a wholesale developer switch due to the underlying library improvements that the users have been dragged kicking and screaming into a more flexible system, which is a must for supporting both the type 1 people and the types 2 and 3. Plus any annoyance generated has either been blogs-full-of-ads whoring or else has been reacted to by the KDE developers and sorted, or at least steps have been taken so that they become sorted some time in the future ;)
The alternative to the kicking and screaming approach is to fork. Forking is usually bad news, but unfortunately there seem to be quite a few projects aiming to address deficiencies in Gnome, without actually fixing what they perceive to be wrong with Gnome. For example XFCE tries to use fewer resources, whilst LXDE tries to use even fewer resources. There are loads of custom file managers, panels, window managers, widget systems etc. which each do an OK job, but don't play nicely with each other and so don't quite combine to become teh awesomes as they rightfully should.
Doing things the "right" way, or leaving many opportunities open for others to reject what you've made in favour of something else, is a much harder thing to accomplish than just shipping a vertical, one-size-doesn't-fit-any stack. Lots of standards are supported in Gnome, but a lot of work is happening outside the project and being shoehorned into the defaults later because it happens to use Glib.
I hope the introspection initiative gets the ball rolling for Gnome again, since it's lowering the barrier to entry and allowing customisation through abstractions and introspection which can guide enthusiastic minds into tackling the itches they face without putting them off by archaic languages like C.