Someone might have said the same thing about molecular biology before watson+crick. Neuroscience has been growing with leaps and bounds in the past decade, and, exactly because it is still in its infancy there are very significant low hanging fruit to be discovered as visualization and stimulation techniques are improving and are employed to scale. It actually does look like we will be able to figure out how our brain works in a decade (decades?). Once that is figured out, we already have the computer framework to do massive simulations of the brain.

Allen himself is funding a Brain research institute, so one wonders why he's pessimistic about the future of neuroscience.