Have a walk with a big DSLR alone in shanty town or favelas in the evening alone.
I used a medium format camera for years for street photography in Morocco, urban and rural Mexico, Vietnam, Italy, Spain, and France. Not once did I have a problem.
For me Iphone delivers some crappy quality level
Then you need to learn how to use it better.
and can not regarded as serious photographer.
Plenty of people have no problem being serious photographers with a phone camera. See the references to Brad Evans' work above. Serious photographers are not made by their equipment, that's a naive and very limited view of photography. Equipment is a very small piece of the equation for "serious" photography.