The core of war has not changed. That is why it is still war. It's a selfish act, full of violence and chaos that does more damage than good, and changes the course of history, however its face, its reasons, its methods, and its appearance have all changed. It's no longer about the issues that caused past battles. It's no longer fought the same way. It's no longer primarily country to country. It's no longer constrained by the same rules.
At the very center it is the same, but everything above that has shifted.