As a longtime reader and editor of P.I. fiction, I commented:
The P.I. novel and protagonist are flexible by nature. Because the investigation is private as opposed to official, a character in any walk of life can do it. The only quality needed is the determination to stay on the job (or go back and finish the job after licking one's wounds).
There have always been and will always be characters looking into things as a favor to others. That's the private eye in essence. Only someone who has a narrow view of the P.I. to begin with (usually Chandler's model) would say the P.I. is dead.