War is anything but profitable. For every additional laborer you create to shoot enemies, or working in factories creating bombs, you have to acquire the capital to build said bombs and pay said soldiers.
Bombs are expensive, yes you might make a single company rich making them, but you are making every tax payer poorer by extracting the money to pay for said bombs.
Soldiers are also expensive, and you have to train them, clothe them, and feed them. This costs money. Multiply that by hundreds of thousands or millions of soldiers.
Not to mention that you are taking people away from productive jobs by turning them into killing machines. Aside from the soldiers that will die on the battlefield, a veteran commits suicide every ~1.5 hours in America. These are young men just getting ready to enter the workforce as skilled labor. They are stunting the time they would spend training and learning real skills to instead learn how to murder people in other countries. For every military skill that will transfer into civilian life, ten more will not. Veterans around the country are already having issues finding jobs after quitting the service before you even account for their PTSD and other symptoms of war. Most market innovations are discovered young, or when older, through knowledge learned when young. Not to mention a man murdering people abroad is a man who is not having children and raising a family at home, leading to issues such as autism when their wives have children when they are older.
You might claim to offset this loss of time developing by giving them "free education," and "free healthcare" for their injuries, but they are not free. You have to extract that capital from business owners and civilians. Every time you take that $140,000 from a business owner to pay for a soldier's education, you have prevented them from investing in 3-5 new employees who would have learned skills to help the nation's economy.
It reduces the Male:Female ratio, but it does not reduce the population in the short term since soldiers returning home are much more likely to have children than people living normal everyday lives. Additionally, you are creating broken homes with dead fathers or abusive mothers by screwing with the gender ratios. In the long term, the higher female ratio leads to all sorts of degeneracy like what we are currently experiencing. More women working = more women influencing politics since politicians are, in theory, trying to extort as much as possible from the taxpayers (those who are working). Long-term this leads to lower birth rates and all sorts of issues as women gain power- you can witness this firsthand in Europe and America. Europe and America do not have population problems and do not need to reduce populations.
Wars of self-defense are just. Without the utilitarian argument of wars being economically healthy, or the myths about war making men more politically powerful, the argument of war being just falls flat on its face.
Defending yourself from foreign invaders is just. Glassing an entire region because you happen to not like them is not- especially when you started the decades-long conflict in your attempts to acquire oil and help political allies abroad gain power. Invading another country defends no one's freedom- it only expands the powers of the elite to control you through various war-time laws and infractions that never end since you are constantly in a state of war, or which become the norm since the state indoctrination centers are teaching your children that these military-state laws are necessary.
False. Competition brings technological innovation. Competition can happen on the homefront or it can happen with other countries. Japan has shown this repeatedly by inventing new technologies and innovating old technologies, despite having not been in an actual war in decades. The economic boom of the 1990s also disproves this idea, as it was largely a "peacetime" economic boom. The Cold War did not bring innovation because of war, it brought innovation because of competition between the East and West.
If you want to get new technologies, think of ways to compete and encourage other countries to compete with you. An international robotic olympics is a far preferable means of developing new innovative technologies than bombing sandniggers.