Almost all of the decline in opportunity that you describe comes down to the massive shortage of housing which has driven up prices. This is caused by planning restrictions and the legal ability of objectors to stop development, and population growth at alarming levels.
When I was born the UK population was 50 million. It is now officially at 68 million and really much more - probably at least 75 million.
Shortage means that people have to outbid one another to secure a purchase or a rental. This sucks out of their pockets a very large amount of disposable income and they are consequently much poorer.
The only answer to this is to cut migration, reform planning and for government to take development by the ears and drive it forward with huge investment.
Rayner is completely right to say she will reform 'Right to Buy'. It was a huge mistake, but it is NOT the major cause of housing shortage. All those old council houses are lived in now. They are still houses in occupation.
You've posted this argument before but I've never really engaged with it fully enough, but this time I'm going to, by disagreeing that migration is such a large element of the housing shortage. In fact it is so far from it that it contains within it a reminder, that we the native population are the largest element of the problem.
The largest element I've hinted at are the the huge changes in our society that have resulted in so much single occupation of homes. In London almost one third of all homes are single occupancy and the rest of the country is not far behind. A small proportion of that is under reporting, but mostly very short term so having little effect.
That, not immigration, is the largest change since you and I were born, which was when multi-occupation of almost all homes was the norm. Most people married and had children. Many of those family homes contained a grandparent and/or sometimes a now adult child. Marriages commonly lasted until death.
Now huge numbers never marry, remaining single or only having partners, often short term. 42% of all marriages end in divorce and a very high proportion of the remainder end in agreed separations without bothering with divorce.
Yet all want their own home.
Immigrants are largely the opposite. Most still marry, especially the Asians. They commonly multi-occupy their homes with two or three generations. The more recent immigrants, including many boat people, almost universally multi occupy, even to the extent of gross overcrowding and "hot bedding". Thus they remind us of where we went wrong.
Take three friends of mine:
"P" grew up in a five person family council house. Now they are the sole person in that same house, but bought long ago under right to buy.
"A" grew up in a six person family council house, otherwise identical to "P", now alone in the original house.
"S" grew up in a six person family council house, but now as above via right to buy and a divorce.
And then there's my family, originally peaking at six persons, parents and four children in one home.
My mother died long before by father so he lived alone in a substantial home for a long time.
My brother married twice having two children by the first wife. She died very early after which he was alone for many years. The marriage to he second wife didn't last long and there were no children, so he lived alone in his own homes for around half his entire adult life.
I remained single for life in my own homes.
My first sister married once to an older husband having four children, He died early, but my sister, like me, is long lived so she has been alone in her own homes for decades.
My second sister married twice with a separation in between, but had very little time alone in her own home, so was the exception in the family.
And then there's the estate I live on. Originally designed with all family houses in the late 1950s in the hope of getting permission to build on one time disputed green belt, building started in the mid 1960s. The huge social changes at the time meant the developer changed and the planners agreed huge changes. The inclusion of a church was scrapped as it became clear that the young of the time wouldn't be going to church and several hundred one bedroom flats replaced plans for far less houses.
All this was done in such a rush that they forgot to change the planned second primary school, so we have that large primary school surrounded with a sea of blocks of one bedoom flats and no family homes, so all the children attending that school are driven there from elsewhere in hundreds of cars. This alone shows how enormous the effect and costs of the societal changes have been.
.