According to OECD [1], population growth outran capital, housing, and infrastructure. So it's kind of like they didn't have enough "slots" to plug all of these additional people into.

They don't claim this is to only or even primary cause of Canada's weak per-capita GDP growth though. As you would expect, there are many, many causes.

[1] https://www.oecd.org/content/dam/oecd/en/publications/report...