I don't know when exactly it ended but I'm quite certain there was little time to continue experimenting with socialist schemes when one is under attack. Industry needed to be able to function in order to produce everything required to win.
And, yes, war is NOT good for the economy or anything else, other than repelling invaders. When all your shit's blown up, you ain't got shit.
I figure that without the wars of the 20th century, we'd all have twice as much wealth, if not more.
Well, yes and no. The position the US found itself in after WW2 was that all its rivals (Britain, Germany, Russia, Japan) had been devastated, and all its factories were fully intact and geared up for mass production. Not such a big leap from tanks to construction machinery, jeeps to cars, bombers to airliners. The Marshall plan was about kickstarting export markets, not altruism.
So on the one hand, you are right, war is a destroyer of wealth. But on the other hand, the US benefitted enormously from it. The net effect was to concentrate wealth that would have existed in territories of its rivals to it.
We are told the Marshall Plan worked wonders. But interestingly, two countries that were both enemies ended up with very successful economies. And both were bombed pretty hard at the end of the war.
Which makes me think that a nation's culture and the freedom its citizens have to take risks and benefit from doing so are more important than handouts. But you could probably guess I was already pretty biased in that direction.
Not to mention twice (or much more) as many people. Oscar Schindler saved over 1,100 Jews from death, and there's over 5,000 or 6,000 descendants of those survivors today. Can't remember the figures exactly, but it's a lot. And of course, with more people, markets are bigger, potential workforce is bigger, which leads to more wealth, which dovetails nicely with your point about wealth.
War productions does not make prosperous societies simply because the allocation of resource is redirected to military purpose, not to civilian needs.