The level of knowledge of civics, current events, and history, not to mention the level of civic responsibility has done nothing but go down since this nation was founded. This idea might have been more tenable 200 or even 100 years ago.
The jury system is an entirely different problem space. There the decision is made based on a relatively narrow pool of information, and is in fact constrained to that pool of information and the personal experience of the individual jurors.
Congress is a whole other matter. There decisions must be informed based upon a vastly greater background of knowledge and, dare I say, wisdom. International affairs and history, broad understanding of current events, economics, knowledge of our system of law and jurisprudence. Do the individuals in congress all meet this standard? No. But the process of putting oneself and one's knowledge and experience forward to the voting public does act as a sort of filter to weed out people who have no understanding or ability to govern.