I'm sorry, but I haven't had time to read the whole thread, but I trained as a nurse in the 1980s, and we would have been in the worst possible trouble if this had happened to a patient in our care. I am imagining what my first Ward Sister would have said to us if we'd left a patient's food in front of them and taken it away untouched, and it's not pretty!
A few things that I think helped, back then.
Firstly - ward design - most of the wards I worked on were the long, Nightingale-style wards, so all the staff could see if someone wasn't eating their meal or was having difficulties - that is not possible now with lots of small rooms - staff just cannot be in more than one place at once.
Secondly, whilst patients did fill in menu cards, the food didn't come up individually plated, it came up on big serving trolleys, which were plugged in on the ward, and the nurse in charge dished up the food - this meant that if someone was admitted after the menu cards went round, or was off the ward in theatre or x-ray or whatever when the menus were done, they could still have a meal, albeit maybe not their first choice of food.
Thirdly, as others have said, there was less paperwork for the nurses to do, and they had not yet taken on as many medical roles as they have today, so they did have more time for the basics of care - plus there were student nurses on every ward, and they were a full part of the ward staff, not supernumary staff, and they had responsibilities for patient care which I don't think nursing students have nowadays.