As we have found out, Brits won’t do some areas of work.
As I've said there's more jobseekers than there are jobs...
And most people would do those areas of work. The problem is, as you note, the lack of social housing. People can't afford to do low paid jobs (also working conditions are often poor, so the answer is to not go after pensioners but instead improve working conditions).
there are too few paying tax
Everyone pays tax, working or not.
Older people don’t often contribute to this.
Yes they do. They worked for decades. But they also continue to pay taxes, even if not income tax. Purchasing goods and services. VAT, and also that's helping keep businesses afloat and people in jobs.
Also there are more ways to contribute to society than financial.
Many people chose not to buy
Very few people chose not to buy. The security and future equity mean most would buy if they could afford to. If someone doesn't buy it's almost always due to inability to afford it.
Unless you mean the minority of people who could've afforded RTB but refused on moral grounds? So they didn't add to the depletion of social housing, because they wanted younger generations to have the same opportunity of affordable and secure housing they had. Hardly something to condemn. I'd say it should be applauded.