You need that immigration since the birth rate is below replacement. Without it the Canadian economy would be in worse shape - and there would be higher inflation. Countries with low birthrates that can attract immigrants will be in better shape than countries that restrict immigration.
Japan has been permanently doomed by economists for the same reason since... the 80's and has yet to collapse. Greater productivity and innovation can offset a shrinking population.
Canada is facing a huge brain drain to the US, for highly paid and in demand professions like in healthcare and tech. It remains to be seen whether or not they can replace the lost productivity of their native expats with mass immigration.
