The government's goal is to use the population growth to prop up real estate while suppressing real wages. They were never ignorant. They were intentional.
What you are suggesting is the opposite what they are trying to do
Exactly. Immigration has been a massive wealth generator - but only for a subset of people who own businesses, land, and real estate. That wealth hasn’t been fed back into the NHS or public transport, it went into their pockets.
Where is this goal documented? I’ve seen some very counter productive immigration policies in the EU, but using migrants as a way to preserve asset prices and suppress real wages is as creative as thinking the earth is flat.
Politically, there are a lot of promised benefits that need to be delivered to old people and fewer and fewer working hands, meaning higher costs to deliver those benefits since labor prices rise.
This would necessitate larger than desired tax increases on the politically influential.
Solution: Reduce the quantity and quality of benefits as much as politically possible, but also import more working hands to reduce labor prices. That it helps support asset price increases is just an added benefit.
That is always the goal with unskilled immigration. It’s not a coincidence, for example, that in the US the Koch brothers and some conservative think tanks opposed closing the border as Trump was clamping down on it. They too like labor to be cheap - their wealth depends on it.