Firstly, ageing population. In 1970 there were four workers per pensioner. Now it is 2. This is because people are living longer, but the retirement age has not gone up enough to compensate for this (and it is debatable how much more it can go up really as some older people will be too sick to work past a certain age, especially in physical roles - we have also encouraged most young people to delay working for years to study too).
Secondly, unreasonable expectations about what healthcare can and should achieve. Both my grandmas had heart bypasses in their eighties on the NHS - one died soon after as was not that fit and heart still failing, other was diagnosed with dementia and had that for 10 years and was in a bad way for a long time with round the clock care. Honestly, it would probably have been better for both of them to have had a massive heart attack, as in times gone by. That sounds heartless, but the truth is that whilst we have managed to increase quantity of years lived, we haven't managed to increase the quality by nearly so much.
Thirdly, we locked down hugely and paid people a LOT of money to stay at home. In the US, they gave people money to keep them going enough to pay their bills/subsist rather than giving businesses money. Some businesses folded, but then they have spent a lot of money on stimulus coming out of the pandemic and the economy is on a roll. Those businesses that were no longer viable post covid have gone in the US, those that are still viable have come back again and new jobs and businesses have been created with the stimulus. We instead followed the European system and kept zombie businesses afloat with furlough and bounce back loans and some are still struggling, especially in the inflationary environment that has passed. Labour would also have spent this money, perhaps even more on income subsidy as the self employed gap was loudly bemoaned by them. We ultimately spent a lot of money on lockdown to prevent rationing healthcare in the pandemic to, largely, older people (who would have been the people turned away from overwhelmed hospitals, as in Italy), only to end up basically being in a portion in which healthcare is being rationed through the whole population post pandemic because we can't afford to invest more in healthcare.
Fourthly, we have a massive productivity crisis - public sector productivity has declined since 2008 and no one quite knows why this is. Some of it may be about headcount being in the wrong place, some Brexit, some about workers being unable to afford childcare and struggling to juggle work, demoralisation since austerity. Private sector productivity is lumpy and we don't have a strategy that incentivises high value manufacturing jobs that would bring more wealth across the country.
Across the whole of the economy, we have created a tax system that has cliff edges that disadvantage and discourage more work - the child benefit cliff edge and the cliff edge at £100k mean that people are often working for little benefit or are even better off cutting hours and paying for less childcare than working. Similar issues around withdrawal of benefits. The same for businesses - we have a high VAT threshold that means that just at the point at which people have a successful business that could hire another worker they have to add VAT - the threshold should be much lower and gradual so that people are not incentivised to stay below threshold to compete with similar businesses.
In my view, neither Labour nor the tories wants to do the hard stuff that will make a difference. The tories are more at fault as they were in power. However, anyone who opposed Theresa May's social care plan to use wealth to fill the gaps in social care in a progressive way is an absolute idiot, so Labour and the Lib Dem's (who branded the plan a dementia tax) can carry the can for that shitshow that is massively crippling the NHS and local authorities.