I liked Mitch’s response the most. He’s uncovered why Maeda’s comment was controversial. Design is a very large and varied field these days, yet some people still equate it to visual design only. When we don’t all know what “design” means, of course there are going to be disagreements about its role in leadership.
Nobody else here has touched on the important point that it’s a designer’s problem solving ability and focus on user experience which is what equips them so well for a leadership role. If your company is developer-driven, you get cool tech and features that nobody wants because they don’t solve a real problem, or they don’t solve it correctly. Designers represent the needs of users in that regard, with the unique ability to transform a customer’s needs directly into a visual experience, that can then be tested and revised cheaply before it even get’s into the hands of development.
For me, the important takeaway is balance. No one prong of the product development process should be too dominant over the other. They all have important roles to play.