But your question is revealing – it shows that society’s expectations of central banks are still excessive. In one respect, the fact that the ECB is independent of political constraints means that everyone pins their (unrealistic) hopes on it in terms of economic policy. But this is unreasonable!
4  BIS Review 128/2007  Recent monetary policy actions The financial shock of 2007 and its potential threat to the economy changed the view held by the Federal Open Market Committee (FOMC) of the most appropriate stance of monetary policy. The stresses led to greater financial restraint on economic growth. Impaired price discovery impeded the flow of capital.