Since no one else has answered in two months, I'll get the ball rolling. Obviously, I'm a "Single-Issue" writer, so I'm a bit biased, but I truly believe that Canada's biggest social problem is homelessness and poverty.
According to U.N. Law, housing is a human right, and according to my research, very few of the homeless are lazy or addicts. in fact, over 60% of the homeless in my own city are employed.
An example of why this issue keeps going unresolved: There is a high level of reserve homelessness, i.e. homelessness on native reserves. The provinces refuse to fund an on-reserve homeless program because Indian Affairs is Federal jurisdiction. Feds refuse to fund an on-reserve program because homelessness is Provincial jusrisdiction.
Because of poor data, or no real research, just actions taken on assumptions to appear popular to the "common everyman" nothing in the end ever gets done to help this group of people in need.