Technology is just one asoect, among many that really help distinguish it.

You had the massive, widespread use of machine guns as an integral part of the armies involved for one thing. They may have been used before, but not on the scale as seen in WWI.

Aircraft and tanks also made their appearances in WWI. Aircraft especially were a major development that completely changed the face of war. Tanks did too of course, but their impact was not as great in WWI itself as aircraft. Aircraft also developed at a faster rate than tanks throughout the war as well. With aircraft, you now had a way for the first time ever, to truly engage your enemy well behind the front lines. Not just the perhaps a few miles range of artillery, but truly reach out and attack even manufacturing and even cities that were well beyond the front lines and would traditionally been considered completely out of reach in the past. Also, aerial reconnaissance offered a birds eye view of the enemy's positions that could be invaluable. You were no longer limited by line of sight from the nearest available high ground or even observation balloon. In a war like WWI, especially on the Western front, where you couldn't really just head out and take a peak a few miles out with say, recon cavalry due to the extensive nature of the trench networks, you can see why simply going over the trenches was hugely valuable.

Again, that's just one aspect, and there are many others such as the sheer scale, political reasons, and of course the road it helped pave for WWII, and it is just a basic post on that one particular aspect but if you have any further questions just let me know and I'll reply after I've woken up or after work, as it is very late here and I must be off to sleep. Hopefully in the meantime others can elaborate more on all the various reasons it stands out.