That's true, but a lot of those same students also end up staying in Canada and getting jobs here. Some of their earnings may even go back to Pakistan as remittances (at least, I can tell you for sure a lot of my friends who came on student visas are sending some money back).
It depends on your field. I know for a fact that DevOps, CI/CD, software developers, etc, have good prospects in Canada and the US. Engineering is a hit-and-miss, but you're generally OK if you're in nuclear, semi-conductors, etc, but I hear civil's tough for some reason. Back in my day, business (esp. finance and accounting) was huge, but it isn't as promising as it was say 9-12 years back, you're better off moving into software development or engineering.