Of course it is possible to survive when SHTF in urban settings, I survived together with many other people.
But point is that many many people died there, other suffered violence, hunger, fear, desperation. Me too.
And you simply need to prepare yourself to do some things that you maybe not like in order to survive. Are you gonna forced to do that things if you are (for example) in rural settings? Sure, but much less, and with much more success, less risk for you etc.
It is simple math, too many people and not enough resources mean more violence, bigger chaos.
And it is not about is it possible, it is about what is easier.