The thing that pissed me off was the lack of coordination between different departments. Comorbidity is not a rare occurrence, and it's not unusual that patients may be waiting to be seen by more than one clinic. But then you get a letter with no details of what the appointment is for, and a separate letter to tell you how to create an account to change appointments and and you can't be sure which it is... and I was just dealing with one hospital, though separate departments. How people manage when they have more than one hospital - that must be even more challenging.
I'm intelligent, used to dealing with bureaucracy, work in IT, so technically competent- and I found it a struggle to work out what I needed to do when. How people who are not well educated, or living with a cognitive disease or struggling to think because of on-going pain (things you might see in health are,) how they manage, I don't know - well, I do, because there are missed appointment stats, but I'm willing to bet a good percentage of these are because of miscommunication rather than patients can't be arsed.
I had one letter telling me my gynae procedure date had changed and would now be a phone consultation. I did ring to ask if that were really the case (even if I were prepared to flash my bits at the camera, without a speculum and lighting, it would not be helpful for the investigation,) and they said that the wrong letters had gone out for that day. Now, I don't know if I'd have got a second correction if I'd not called to query it, but I suspect that they would have had a few patients that day who were no shows because they were at home waiting for a phonecard which would never come.
It would be far better for both staff and patients if there was a lot better admin, coordination, and communication in the NHS. It is technically possible, but not without investment, and there have been too many years without that.