Thanks for pointing out Alex's article, it was a worthy read and interesting perspective.
From a designers perspective however, I agree with you. Irrelevant to what percentage of design ideas actually manage to make [hugely] social and/or ethical impact, it should not stop us trying. In the apt words of Jeff Mauzy and Rick Harriman (2003); "The inventor never got punished for pursuing the idea."
In my opinion, the IDEO/d.school -esq 'design-thinking' from which Alex consistently focuses on, is merely the first positive step for the creative industry and its surrounding societies. Recognising the designer as ‘thinker’ or ‘innovator’ is only the first step of the journey, and for that reason, the future for designers making 'revolutionary' change is still viable.