https://en.wikipedia.org/wiki/List_of_ongoing_armed_conflict...Pretty much all these conflicts are pretty limited and there's very few states focused on war (whereas before Nukes in the 20th century essentially all of Europe and Asia was focused on war, constantly)
So yes, I find the idea that the nuclear weapons threat is preventing a LOT of wider wars and is responsible for the most peaceful period ever in human history pretty convincing.
When it comes to relations between states, arguments go between capitalism and war (ie. just taking what you want vs trade)
I get that capitalism (selling/exporting their oil) brought Soviets enormous success and taking what they want in war brought the USSR down. And yet, despite that, here we are with Russia and Ukraine. You'd think recent Russian history would convince anyone the Ukraine conflict is not worth it, obviously not for Ukraine, but also not for Russia. It's an easy argument to make that for Russia abandoning the war today, just going home right now, will provide more rewards for Russia and Russians than a complete victory would bring, even if that victory ALSO came today ... and yet nobody thinks Russia will abandon the fight. As for their ability to wage war, the sad truth is, Putin has conquered more people than he lost, and Russia has conquered more minerals' than they lost in equipment. If Putin wants to use both resources to create more war, he will be able to do so.
Something very similar can be said about China and Taiwan. Not having a conflict is obviously the best option ... and yet, there's very little doubt that conflict will erupt in a few years, not decades.