Anyone who applies for a temporary residence visa (e.g. students, workers, tourists) has to sign an application confirming that they HAD NOT INTENTION TO STAY permanently.
They have to submit documentation to persuade a Canadian visa officer, per the Immigration and Refugee Protection Act, that on a balance of probabilities, they are likely to leave Canada before the end of their authorized stay. That documentation includes proof of "establishment factors" in their home country, e.g. assets, employment, family ties, etc..
Many are then questioned by a visa officer abroad, and then a visa officer at the port of entry, further to establish their bona fides as a TEMPORARY RESIDENT.
The visa they receive in their passport makes it perfectly clear in plain English and French that they are legally required to leave the country within the authorized period.
Any official IRCC content they read online would make it absolutely clear that they are applying for temporary, permanent residency, and are not permitted to stay.
If anyone can come, overstay, and violate our fair and generous immigration laws, then why not just have an open borders policy? On what grounds could we deny people temporary visas? Because they've been honest about their intentions to stay permanently?
Finally, it is not a terrible hardship to ask people to return to the countries they are from. Imaging that Canada must "save" people from their homelands is a profound kind of chauvinism. Of course, there is a moral and legal exception for people facing a well-founded fear of persecution, but that's what the asylum system exists to determine.