The productivity in Canada is declining coupled with rampant inflation, cost of living increases and Income levels not rising as an offset which is the answer.If they are such a net positive, why are living standards and overall wealth going down?
And without immigration the situation would be even worse. Deport all the immigrants that came to Canada in the past five years and the Canadian economy would essentially collapse.
There are many able bodied Canadians on social assistance who could work but choose not to just because, a resource that could reduce immigration levels somewhat also.