Sure, peace deals are important. But I'm not sure I want to trust this author's take given his view on Versailles for causing a future war because it was too harsh.
One major part of his reasoning is that reparations were so harsh that they caused hyper-inflation that led to support for Hitler and divisions among the victors.
On the contrary, hyper-inflation was a strategy to nullify reparations by making it easy for repaying with debased money. And Germany used the reparations in an information war effort that roused Germans against the Allies and split Western opinion by successfully portraying Germans as victims to a subset of the Western populace who forgot that the Allies were the good guy in the war, amplifying the anti-war people's concerns that World War I was so costly that it should never be repeated--and that concessions to the "wronged" Germany was the way to make sure the war was not repeated.
Indeed, this defense of his view seems to support my view more:
Although the Allies satisfied their shortsighted vengeance at Versailles, they failed to anticipate these impacts of the treaty on German economic, political, and social policy and ideology. English Economist John Maynard Keynes, who attended the post-war dialog at Versailles, predicted in 1919 the peace treaty imposed on Germany would lead to catastrophic consequences because it “includes no provisions of the economic rehabilitation of Europe, nothing to make the defeated nations into good neighbors, and nothing to stabilize the new States of Europe.”
Consider that the World War II settlement led to the occupation of Germany with the de-Nazification of the country, which did in fact compel the Germans to be a good neighbor integrated economically and militarily with the victors. The World War II settlement was far more punitive than the World War I settlement that allowed Germany to refuse to abide by the terms of the World War I settlement and instead attempt to reverse the 1918 losses.
So yes, Versailles was flawed and led to World War II in Europe. But no, Versailles did not fail because it was too harsh. And the harshness of the World War II settlement that physically dismembered Germany and allowed the victors to permanently occupy and shape the German leadership (and Western victory in the Cold War merely changed the "occupying" powers--who in the West went from occupiers to defenders during the Cold War) should demonstrate that very clearly.
There is more of the article's evidence to quibble with.
The division of Korea after World War II wasn't by itself the cause of the Korean War. Our departure and the weakness of the South Korean military that was more of a police force than an army created the vacuum that allowed Soviet- and Chinese-supported North Korea to invade.
The part on Vietnam is off, too. One, the author takes Ho Chi Minh's declaration of independence at face value, essentially blaming America for refusing to accept a Southeast Asian Thomas Jefferson and instead turning him into a harsh communist.
That's an odd Thomas Jefferson, was he not, to be turned from proto-democrat to brutal communist by our limited role in what was a French war?
And two, when we refused to allow a vote that the communists would win and instead sided with France, was France's cooperation in the far more important theater of Europe insignificant when Euro-Communists friendly to the USSR and the direct Soviet threat to peace in Europe were so high?
Further, you have to consider the effect of the time we bought in a losing war. Losing Vietnam in 1975 was better than losing it in 1965, 1955, or 1945. As in Europe, communists were pressuring weak states from India to Southeast Asia after World War II. The non-communist states were able to use the time blunting the spread of communism to build up their societies, governments, and economies to resist the appeal of communism.
So yeah, the post-war peace settlement is an important component of securing a victory won on the battlefield. I'm fully on board that cautionary tale by the author.
But I think the evidence used to make that point shows the importance of getting the right kind of peace settlement. I don't think the solutions offered to the so-called problems would have solved the post-war failures cited.