If you put only designers in charge of any kind of a project or organization, you just end up with a different kind of disaster. Look at GNOME 3, for instance. It was a design-led initiative. It failed to produce usable software, it failed to attract any new users, and it actually managed to drive away an absolutely huge number of existing GNOME users. As it stands, it is one of the worst OSS disasters we've seen yet.

You need a balanced team. That's the only way to truly succeed.