Indeed, obviously no huge organisation is 100% efficient, but I don't know if the NHS is 95% efficient or 90 or 70 or 50...
People extrapolate wildly based on very limited experiences.
E.g. When I was in hospital an old man opposite with a broken leg was deemed fit to discharge home, as they needed the bed. Clearly he was very frail and unsteady and would fall over. Two days later they readmit him with a broken collar bone and arm as he did fall over. Wasteful. But I don't know how often that happens.
Similarly my kid had his eyes checked at school and he plus several classmates were told to go see an ophthalmologist at the hospital for an hour appointment. She took one look and said he was fine and it was a waste of time. But I don't know how often this happens.
In all these political and societal matters you need to cast your mind back to the 70s and early 80s when Britain was crushed, impoverished, no services, on strike, brutal. Things are flipping MARVELLOUS nowadays