Those things matter a lot more than the exact funding model. And they sure matter more than how many people come to live in the UK.
Theres also the fact that the number of people aged over 85 has quadrupled in the same period.
Im an NHS staffer, and I believe in the NHS public funding model because I think it’s efficient (to me, about the last thing we need is a whole load of new insurance gatekeeping admin around going to see a doctor). But where the money comes from hardly matters compared to having enough GPs, enough District Nurses visiting people at home to keep an eye on them for GPs, and having some actual beds available for those GPs to admit people to. That, of course, and community services to discharge people to, so that the acute beds stay open.