Why can't we demolish every residential structure under 5 stories tall in central London and build flats? Why can't you build in the green belt?
There are some good reasons - the negative externalities of one-off housing in the middle of nowhere are huge (I say, writing from a one-off house in the middle of Ireland), but there are some bad reasons too, like homeowners using "social and affordable" to concern-troll their way in to ensuring nothing actually gets built.
And yeah, dev salaries in the UK are shockingly low compared to the US (and Ireland for that matter, so far as I can tell) but when the supply of housing is constrained higher incomes don't help for long. Making $250k might enable you to buy a $2 million 4 bed 2 bath near decent schools in San Jose, but give it a while and you'll need $350k, then $450k, etc. (or remote work will break the back of the NIMBYs with any luck).
These are not just first world problems. These are problems that could, potentially, destroy entire economies.
Immigrants will soon be facing the same issues (high housing, high education costs, lower wages).
I reckon in about 20-30 years the arbitrage opportunity to immigrate to Western countries will be eliminated, it already is much reduced compared to 30 or 40 years ago. QoL in Western countries will be lower, and higher in the rest of the world.
I often think of a documentary I saw about Somali refugees who came to America in the early 2000s (sadly I can't find it anymore.) They ended up moving back to Africa because they hated life in America. Working two terrible minimum wage jobs just to pay rent and food. They made no friends and had no free time or money.
They were happier living in a UN funded refugee camp spending time with friends and family.
I think the only way Western countries have any chance of reducing the falling QoL is space exploration, but I don't think their is enough energy and motivation.
If I buy farmland and build a house in Ireland, I know I'll be forced to demolish it after my neighbours complain (and a long review process). In many places there would be no such enforcement.