We are, but some people completely disregard the reality of the times and speak knowing the outcome. This is what's annoying. During WW2, people didn't know the outcome. The decisions we see as mistakes today could have been absolutely reasonable, or even the only possibilities, back then.
Yamamoto did advocate against war with USA, but at the same time he admitted there is a chance of victory given that the war is concluded with a few decisive strikes and a favourable treaty. It was reasonable, and it was probably the only possible option for Japanese given their imperialistic ideas. That plan failed in the end, but not because Pearl Harbor was a mistake, but as a result of the economical inferiority, and ultimately because of a string of bad luck and bad decision-making.