They never will. And frankly, it wouldn't do what you may think it would.
The United Kingdom has acknowledged its colonial legacy to the point that it's committed a kind of geopolitical suicide as recompense for 250 years of global spanning Empire. Has acknowledgement of its history made relations with other countries easier? Not at all. Because the UK's former colonial holdings (the troublesome ones) really aren't interested in letting bygones be bygones. Really they want nothing from the British at all, other than to fuck right off. If anything they want things the British can't give.
There is also the ongoing question of how responsible are people for the crimes of their forebearers. As we move further and further away from World War II and the Colonial era, that's going to become more complicated. Take for example the American expansion westward (which is what the US did during the age of Colonialism). Am I responsible for the native American genoicide and displacement, even though one half of my family didn't arrive here until the 1890s and the other didn't arrive here until 1946? Are Germans born since 1990 inheriting the responsibility for the Holocaust and World War II?
Politicians in countries pull on these strings for political advantage, but they really aren't looking for a resolution. "Japan the Unrepentant" will forever have more currency in neighboring countries than "We're good with Japan now", because people will have heard from their grand parents and great grandparents of what the Japanese did.
So in the end, what's the entire fucking point? As ever, money and control. South Korea and Japan can both be mollified through this route. It is a transactional relationship.
You understand these points, yet you dont aknowledge that identity politics of the left is bullshit and all about control.