The technological innovations that were made over the course of World War One were incredibly significant. New developments in weapons, such as long-range artillery, the machine gun, and the tank made killing much more efficient. The reason for the millions of deaths in the war was because civilian leaders and military tacticians were slow to adapt the previous century's tactics to the new battlefield realities that these weapons posed. The idea of masses of men charging straight toward enemy lines might have been effective during Napoleon's time, however, it was devastating and exceptionally bloody during this modern war given that they were now charging through barbed wire and towards machine guns instead of at bayonets and muskets.
The airplane was also a technological innovation of the war. They went from being simple canvas and wood observation planes to armored fighting machines by the end of the war. If you compare the relatively simple aircraft used during WWI to the more sophisticated machines that terrorized the skies a few decades later during WWII, not to mention the development of long-distance cargo and passenger planes, you can see that the war was a major catalyst for innovations in aviation.
All in all, if you make a list of modern military technology, from fighter planes and submarines to machine guns and tanks, you would see that many of them got their start during World War One.