War certainly destroys somethings, but in other ways it spurs invention -- radar, cyrptography, jet engines, computing were all products of world war 2.

And sometimes destroying leads to improvements - the blitz destroyed a lot of slum housing in the London east end, which was rebuilt en mass in a way that wouldn't have been possible without the widespread destruction.

Massive losses felt across the population in the UK led to a national unity and a desire for improvement of everyones lives, leading to things like the welfare state and healthcare for all.

Looking further back in history, the US war of independence is deemed to have had desirable outcomes.

You can still think war is a failure but acknowledge that it can lead to benefits as well as drawbacks.