There are still a few alive...and it’s just one issue on a whole list of massive grievances Japan’s neighbors have that are even on a graver scale. That’s like saying Germany shouldn’t have to acknowledge something like the Holocaust because there aren’t enough survivors left.
The past is the past. The Japanese were repaid for their crimes in the form of atomic bombs and fire bombs, occupation and fairly humiliating peace terms, in addition to the government acknowledging Japan’s atrocities and paying reparations. They’ve managed to become the 3rd most powerful economy on earth and for all their problems, have retained a strong national identity. Would you rather they acted like Germany, never mocing on from the past, slavishly suicidal, terrified of being accuses of harboring an iota of national pride?
A Korean co-worker, when asked about the success of Korean industry often said ‘Korea is a poor country that has good water, the people work very hard and they hate the Japanese’.