Writing code in leisure time has given us some really great FOSS applications. But like many things, it's a double-edged sword: it's also given us Gnome3 and a lot of today's unnecessary churn. However, unlike little 1-man projects, Gnome3 isn't just a leisure-time project, it's largely led by paid developers at Red Hat. So honestly, I'd say that the volunteers really aren't the problem, and if you eliminated the salaries of the Gnome devs working for RH, maybe we wouldn't have some of these problems; the volunteers aren't going to sustain all that effort on their own. The commonality I see with UI churn across the industry (proprietary and FOSS) is that UI people are being paid to do UI work. That means they have to justify their pay and their existence by doing more such work, even when it isn't needed and it's downright bad.