In the book Ministry of the Future, a near-future look at a world dealing with devastating climate change, wars become somewhat obsolete because drones get so good it's always possible to kill someone anywhere in the world. The smallest faction can easily kill the leader of any country. It's an interesting thought. I don't recommend the book, one of those thought experiments with lots of interesting ideas with not enough story.
It's fallacious to assume that defenses stop evolving after new weapons come to the fore. Some drones are deployed in anti-drone capacities; the war economics becomes balancing how advanced to make the attack drones vs. how cheap the countermeasures are. In Ukraine we've already seen small drones that are able to damage the wings of much larger and more "technically advanced" platforms.
War didn't end the first time man invented the longer spear; defenses adapt.
