Its not purely about the gear, but there are photos you can create with a DSLR that would be impossibe/difficult on an iPhone.
This photo of mine for example:
It took a lot of trial and error and dialing in the aperture, ISO, and shutter speed in order to get this photo. That level of control doesn't exist on an iPhone. Nor does an iPhone have the massive lens, big image sensor, and signal to noise ratio that would result in the quality.
I also shoot a lot of astrophotography, which requires a lot of fine tuning as well, and again would be practically impossible to capture with an iPhone.
The gear doesn't make the photographer, but it expands on what the photographer can do. Its completely possible to take excellent, pro-quality shots on a modern smartphone, but only under certain circumstances. The flexibility, adaptability, and customization that DSLRs offer allows good photographers to do more under a wider variety of circumstances.