everybody who ever spent their lives making weapons wasted their time.
An naive and arrogant point of view at best. We live in a world where a person merely crossing the street is subject to being ambushed by rapist gangs who are impossible to negotiate with, and the international relations between some countries are just as bad, way more complicated, And only well-informed officials and strategists can give an idea on how to keep us free country citizens safe, but one thing is clear: Good Weapons are always necessary. More efficient higher tech weapons allow for a better result most of the time, especially when destroying opposing military equipment with fewer human casualties on both sides. Weapons serve as both a means of destroying equipment, and weapons and weapons manufacturing facilities are also targets to be destroyed. And at least so long as facilities and not people are targeted - the toll of war involves fewer lives and more money being lost in that equation.
As a person living in a free country and reaping the benefits of living in a free country: You also have a duty in the defense of that society by being a citizen that is an inherent part of the social contract which has allowed and continues to allow free countries to even exist in the first place and not be automatically conquered by whichever conquerer is strongest and most ruthless at the time. If the needs of the defense of our society requires going to war, then the duty of All citizens, even you is to contribute your part. Whether that ends up as by being pressed into military service through drafts, etc, building weapons, contributing special skills if you have any that are demanded by your country, Or by just by paying income taxes.. None of that is a wasted endeavor by those contributing, And you have your very life to thank for the efforts of people making weapons.
Considering many of the weapons people spent their time on making saved countless millions of innocent lives. It's a very real possibility many of us would not have been born if not for the effort in the development of certain weapons. Despite it is true that usage of weapons in war comes at a human cost, and we face a grave risk of demise at the hands of the ultimate weapons of mass destruction. Better tactical weapons in many areas that more accurately accomplish military objectives (Destruction of opposing military infrastructure, As-opposed to people) also reduce collateral loss of life.
However, as mere engineers or tech workers. We are not actually involved in making nor equipped to have a great understanding in the decisions about when and if war on our country's part is an obvious necessity; Nor are we sufficient experts in strategy to know the right path -- that is a matter for our generals, and commander, etc, to debate the complexities of our predicament at a given time.
World War II, and the US involvement in Europe was obviously necessary, and now we can recognize that retrospectively. But at the time that was not obvious whatsoever to the public. Indeed the US entry to WW II was very late and probably cost 40 million lives that could likely have been saved with much earlier preparation and entry to war.