the low vacancy rate are due to high immigration and low supply.
it would be nice to build more apartments, but the political system is stacked against it, which is why it's not happening. it's not happening due to an insufficient supply of labour. it's not happening because single-family property owners elect city council members that block it. rich people hate renters and don't want them in their wards.
so, it's a lot easier and more realistic to block immigration.
the basic point is that immigrants benefit the wealthy at the expense of the poor. that's the economics of it. all of the arguments in favour of immigration are good for rich people - it's true - but bad for poor people. the second part of the argument gets lost because the media doesn't care about what poor people want.
the ndp pretends to represent the poor but their policies consistently benefit the rich.
it makes sense for ndp voters to swing right on this issue and that shift isn't going to lift with rhetoric or reverse any time soon. this is about class interests.