doesn't matter what system states use, there will still be war... it's just human nature
No, actually, it's not. Do you want to kill your neighbors? Very likely not.
Interestingly, history shows that in shooting wars, soldiers have shot to kill at a very low rate - there's a natural aversion to it.
In fact, we've modified military training to concentrate on bypassing the thinking parts of the brain to get ignored in battle and shoot reactively.
Some speculate that this has contributed to the increase of PTSD as soldiers come later to deal with the violence.
Actually, war is an organizational problem. Much as one person might like another person's belongings and could use violence to take them, but hopefully decides not to do that, nations are incented to pursue power and wealth at the expense of others, but you hope to find ways to have them not do so. The US could technically profit by conquering Canada and taking its resources, killing or enslaving its citizens, but we don't want to do so.
But there are times war gets a momentum going for various reasons - sometimes for little more than an opportunistic gaining power by stirring the flames. Often it's because of concerns about shifts of power going on. I could provide a long list of examples, but will defer that for now, hopefully it's not needed.
That's not a 'human' issue, it's an organizational problem, much the way any group of people can have 'organizational' problems. Big corporations often do things bad for society because their charter is to seek profit not only by building better mousetraps, but by doing things good for them and bad for society. They're legally compelled to pursue such interests. Their top management is hired to pursue them and gain as much profit as possible, their workers hired to do as they're told for those pursuits.
Any one of those people might say 'this is not right', but they can not do much about it.
This is a reason why "peace studies" make a lot of sense, and are not just candle-burning singing folk songs against guns. John Kennedy put out a collection of speeches titled "The Strategy of Peace"; he understood that as much as war, peace needs powers to make policy to try go get it and keep it. He didn't always do it himself - he was President at the height of the cold war - but he greatly reduced the risks of war.
Wars are often made up of large numbers of people who have nothing against each other put in the position of kill or be killed for the interests of leaders and the rich.
War is not human nature, but history makes clear that nations can force their people into wars for any reasons they like.
We should try to support politics against wrong war - not throw up our hands as you do.