It's worth noting that while we have 70 years of better technology, we have much less of it than we used to have, and the tech difference isn't that large - machine guns are almost the same, artillery is almost the same, and a ton of conventional bombs is as destructive as in WW2, except more accurate.

The standing armies are generally smaller than the ones before and after WW2, despite three times larger worldwide population. The effective mobilization potential of major countries is much smaller than before or after WW2 as many countries have moved on from total conscription where you'd expect most of adult men to have military training and a huge proportion of the population to actually fight in a war. The quantity of planes, bombs, guns and shells that we can muster is an order of magnitude smaller than 70 years ago, so while each bomb or gun is more effective, the total destructive power is less than it used to be. The world has 5 times less nuclear weapons as it used to have.

So the actual trend is towards a smaller scale of destruction. We have major wars that result in as much casualties as an average WW1 tuesday despite being as full-blown conflicts by the involved countries, mobilizing as much as they reasonably can in modern circumstances.