1) battery: the iPhone was basically a giant battery strapped to a logic board. No one had designed a phone like this, ever.
2) capacitive multi-touch with inertia: capacitive touch screens existed, but the software for using them was really bad (see windows mobile 5 as the leading example).
3) non-WAP browser: all phones prior to the iPhone had a wap browser. The consensus knowledge in the industry was that doing full web on mobile was still years, maybe decades away. Apple came in and rendered the full New York Times on mobile and it changed the world.
4) App Store: before Apple, carriers had an App Store that was garbage or you sideloaded software. That was it. The App Store changed the world, not technically but politically. Finally users could get good software from their phones over the air.
I could go on for days. This doesn’t even touch carrier distribution, call quality, or any part of the OS stack which was basically black magic at the time. The iPhone really changed the world.