I have some sympathy with Flusser's position.
For the last few decades I have been making photographs to give visual expression to states of mind rather than just reporting the appearance of material forms. In photography the real world is the source of those material forms and that is part of the problem. Finding the subject matter with the right metaphoric connotations is a chore and I often find myself resenting subject matter for its ungenerousness. The pay-off is that when the right subject matter does turn up the final pictures, being photographs, carry a power not available in any other medium.
Flusser's preoccupation with the camera goes a bit too far. The camera is an essential tool that has to work reliably but, just like subject matter, film, and paper, it is a necessary nuisance that needs be endured on the way to the photograph in its final form.