Monica, I would not apply my criteria to every person with dementia. However for many years I was regularly visiting relatives with dementia in care homes, and although some residents seemed happy - or at least contented - enough - there were too many who were almost permanently anxious, fretting, or distressed about something - maybe something they could not even name - and could not be comforted.
One that will always be with me was a lady in her 80s who was so often crying and distressed because of ‘the baby’ she thought she’d left at home, or else her mother wouldn’t know where she was and would be so worried. Although the staff were very kind and did their best, nothing could comfort her.
Every time I visited, without fail, she’d be pacing anxiously back and forth with a large packed bag and would ask whether I had a car, and could I take her home.
To me, striving to keep any such person alive, really would be cruelty.