More workers isn't going to help if all the jobs available are below the taxation threshold. Many of these immigrants aren't coming and joining the workforce, they're coming and joining the dole. That's not going to increase the funds for the social security net.
What would help is if the government stopped treating CPP as a petty cash box they can dip into whenever they want and actually funded it appropriately. Let the boomers die out and let the smaller younger generations work. There's not enough jobs right now. We don't need to bring in more immigrants, that won't fix it when there's not enough jobs to go around in the first place. It just means the jobs that remain are lower paying.