On one hand, the fact that a lot of smart people are trying to kill you is a great motivation for rapid technological advance and reduction of red tape.
On the other hand, many of the young men in uniform who were torn apart by shells and mines could have been new Einsteins.
The problem of geniuses dead in wars pales in comparison to the number languishing in poverty or ignorance. These may number in the billions right now.
How many potential Einsteins are miserably toiling away in dead end jobs? How many Ramanujans are eking out lives in villages in India? So on and so forth.
And another issue: if 100 million die in war or 1 billion aren't born due to fertility collapse, which is worse for progress?
Waste of talent doesn't necessarily take the form of poverty and danger. We should be aware of the other part of the scissor, because it means that improving living standards aren't a panacea for this problem.
Hungary 100 years ago, a fairly backward and mostly agricultural country, somehow produced a long string of incredible geniuses that contemporary Dubai cannot.
Think about it: You have a top 0.5% intelligent person. You can influence his carreer choice. You can either pay him a good wage to become a detective, or he can become scientist. If he becomes the former, a few good papers on horse fly entomology won't be written. If he becomes the latter, a dumb detective will cause an injustice that will escalate into an assassination, and a world war.
You got your cars, you got your airplanes, but you got a society in a state of disorder, that lead to the sciences getting taken over by morons as well, and made further progress impossible, with the east asian countries competing over technological superiority.
Tech trees are straightforward to visualize but I challenge you to think of a law tree or social norm tree as well.
IIRC the end of colonialism and thus the end of the associated oppression, is also associated with the world wars, as they left the colonial powers too exhausted to retain their overseas empires.
