"Complicated legacy" is fitting.
On the one hand, I believe Kissinger's realpolitik approach is under-appreciated since the end of the Cold War. "The end of history", spreading democracy to Iraq, believing that simply opening markets would lead to countries moving towards freedom and democracy, ostpolitik... a lot of U.S. and western foreign policy was optimistic. Kissinger was still active as a nonagenarian, and even as a centenarian, and I generally found his arguments on foreign policy in the 2010s and 2020s to be well-argued. I might not agree with every conclusion, but he was putting more thought into it than most and making good points.
On the other hand, he put too little emphasis on retaining the moral high ground. Bombing in Cambodia, escalation in Vietnam, supporting the overthrow of democratically elected governments. There's a time to be realistic and there's also a time to say that you have standards. As FDR once said, rules are not necessarily sacred; principles are. There were a lot of decisions made by Kissinger, Nixon, and others in the 1970s that seemed to fly in the face of what one might have thought the U.S. government's principles would be.
War criminal at his worst, wise statesman at his best. I don't think it's an either/or question. Would I trust 1970s Kissinger to made decisions at the State Department? Knowing what I know now, no. Would I consider his advice if I were Secretary of State in 2010? Yes.
Given 2023's reality, where he only had the power to write and speak to the public - primarily in venues targeted to policy professionals - and to hobnob with world leaders, not to make decisions, I think losing him is a loss. Our memories are short, few remember fleeing the Nazis, dealing with the Soviets, and the decisions, including mistakes, in Vietnam. In a world where it's easy to turn inward and argue against each other, his focus and expertise was outward. And I think that's the important takeaway - his decisions in the 1970s may be inexcusable, but the attention that he gave to the foreign policy realm, and the focus on being realistic and not wishful, is something we should strive to regain.