I think it's a real lack of staff, coupled with the general public's refusal to take ownership of their own health.
My trust is completely dependant on agency staff, which cost at least 3 times more than permenant staff, nearly 1/2 of my 'team ' is agency at the moment. And I don't blame the agency staff as they get paid so much more for doing exactly the same job. The trust has to pay agency as the bank rates are so low, and the alternative would be to cancel operations and that is obviously not going to happen. The long days, rubbish pay and many managers refusal to be family friendly have sent staff away in droves.
There is a real culture of it being your 'right' to access free healthcare even if it is not in your best interests. Plus so many health problems can be reduced, if not resolved by being a healthily weight, being active and stopping smoking. For e.g. knee replacements, the vast majority of those who have knee replacements, losing weight would solve their problems, but when the NHS tried to ration them, there was a revolt and the trust involved was accused of being discriminatary.
I honestly think the NHS is unsalvagable and will not be around in it's current state for much longer. It was never meant to last long term and was introduced to bring the nation back to heath after the war. It makes me sad as I love everything it stands for but I think it is on its last legs.