Well the theory of ending low wage immigration was never tested. As the Economist article notes, low wage immigration is up.
It is not only the Polish or Italian immigrants like me that compose low wage immigration; in fact, non-EU immigration is higher than ever.
And I'm not even touching the fact that immigration is a great economic boost, but tends to be misconstrued as a negative to avoid by politicians, as if migrants come and sit on their arses living on benefits.
It was utterly clueless to expect such big changes to happen overnight.
This goes for Brexit in general. It will take decades for things to shake out and the world will be changing all the while.
But now, any company that did hire domestic workers was left holding the bag and the government created a moral hazard setup on subsidizing being unresponsive to immigration policy changes.