A health care system that is free at the point of care will always be underfunded. That is to say the demand will always outstrip supply, as there isn't the financial barrier inherent in all supply/demand relationships.
If this were true then there would also be long waiting times and huge backlogs in the other countries that also have healthcare that is free at the point of delivery, such as most of the EU countries. Nowhere that has universal healthcare has let the situation deteriorate to the point where over 10% of the population is on the waiting list for a hospital appointment.
As for a financial barrier to healthcare and a supply/demand relationship - this is simply the flawed free market thinking being inappropriately applied to healthcare. No individual can know what their healthcare needs will be - today, tomorrow or at any time in the future - but using collective data and socialised healthcare provision should be able to provide for each individual as and when they need the care.
Add to that the layers and layers of wasteful management, plus superfluous workers and forms, and you get the mess which is the current NHS.
Here's my example of "wasteful management". I know a very capable person who is currently the deputy director of nursing in a large health trust. She has an MBA and several years of non-NHS experience in industry, as well as originally training and working as a nurse and having 20 years of NHS experience.
She should be spending her days looking at how to improve the service, planning for the future, managing the nursing staff, working with HR, trainers, facilities etc. to ensure that her Trust attracts, develops and retains the required staff. Instead, because there is a shortage of beds, a shortage of nurses and doctors, a shortage of nursing home places into which patients can be discharged, a lack of coordination between the Trust and social services (who have their own budgets and priorities) she spends all of her time fire-fighting. Dealing with "today's issues" - such as telling a patient that his operation has been cancelled for the third time (and then dealing with the nurse or receptionist who perhaps has had to face the anger and disappointment of the patient and his relatives), trying to find somewhere to send patients who cannot be discharged and so are blocking beds, trying to deal with staff falling ill or resigning from the unrelenting pressure. On top of which she has also had to cope with government directives to cut staffing levels - at a time when the hospital is already short-staffed and overwhelmed.
There is always room for improvement. There are new systems and technologies that can be used to simplify and speed things up. But none of this works if the system itself simply does not have the capacity to meet the demand. And none of this will improve if managers are spending all day fighting fires instead of planning ahead, making improvements - and nor will it improve as long as an ex-banker (Javid) ex-PR executive (Hunt) or ex-economist (Hancock) are in charge of policy, or as long as the heads of the NHS organisations in the UK are beholden to their political masters.