The question though is this: is a personal signature look harder to achieve in photography than any other artform?
Perhaps, by virtue of the fact that the cell phone has put a camera into the hands of billions of people.
However, your question also prompts me to think about the nature of "achieving a personal signature look". IMO, those who have been/are most successful are usually following their own passion to wherever it may lead, and however it may develop. Too often, however, photographers/artists create work that is either "a copy of" or "premeditated" to look different in order to stand out. And it shows. And when art critics (the mediocre ones) laud and promote it, everyone loses.
At the same time, it's easy for critics to dismiss and scorn work as "derivative", when, in fact, it may bring a new perspective or interpretation into play.
I used to struggle with the notion that I had to "find my passion", develop a body of work, develop a signature look. Fortunately, as an amateur, my subsistence and self worth does not depend on these things
. My hobby spans different genres and interests, and my efforts to create a cohesive body of work often end up with one or two good pictures among a raft of mediocre ones. One day, however, another member of my local photo club told me that she could always spot
my images from among a random group of pictures. "Good or bad?" I asked. "Mostly good, and almost always interesting," she said. I'll take that as a compliment.