We have to remember that the money we pay into our "pension" doesn't pay out pension it is paying for the pension of the generations before us, our parents and grandparents. If there are not enough people contributing then there isn't enough money to pay anyone.
There will be more people paying in now than there were in previous generations, though. More women work, the population is larger, and the state contributions made to women who weren't working because they had children were cut back so that they can't be claimed after the youngest child is 12. Women with children over 5 are now 'encouraged' back into the workplace. It is simply not true that there are fewer contributions coming in than before, and the amount of money paid out in furlough and other Covid expenses is evidence that there has been enough in the coffers to cover the funds associated with the 'we are living longer' argument.
In any case, if the scheme is not fit for purpose that is the fault of the administrators, not the beneficiaries, and needs to be sorted out without detriment to those who contributed. We have paid our contributions in the belief that we would get a pension, and if that is reneged upon then faith in the State and 'the system' will falter. I don't mean faith in the current government, but something much more fundamental than that. Government in the UK has always relied on consensus, and that has to be a 2-way street.