I agree, dementia is something that generally cannot be accommodated at home. Many patients need 24 hour care and supervision, they can be impulsive, sometimes aggressive and a danger to themselves and others. It's terribly, terribly sad but specialised residential care is necessary for them.
An aunt had dementia, she wasn't aggressive but she would wander out in the street in her night clothes and didn't know what she was doing. She could have been dangerous with regards to trying to cook, leaving the gas hob on, that sort of thing. She was very elderly and, reluctantly, my cousin (her daughter), put her in a home where she was extremely well looked after and safe. Obviously she was visited often. She did die before too long. One comfort my cousin had was that her mother was not aware of very much, she was in her own world, so not upset at being out of her home. Her granddaughter brought her to my mum's funeral and she was actually very funny and alert at the wake and then asked whose funeral it was. When I told her she was terribly upset and crying, "My little sister, no". It upsets me now to remember that. However she soon forgot and was OK.
My ex-neighbour's mother was a lot younger, developed Alzheimer's when she was about sixty. Dad refused to let her go away and looked after her at home but she was quiet and eventually stayed in bed most of the time.
Another couple of women I know have husbands with dementia who are in homes. They take their husbands out a couple of times a week, sometimes staying at home watching old videos, sometimes going to a cafe they know, and for a drive but it's always difficult when they are taken back. They are only allowed out on the condition that they get back by evening because that seems to be the time when they become aggressive and their wives are in danger.
A friend of ours had Alzheimer's and died in a home aged 68.
Other illnesses can be managed at home with good care, that is what I would want for myself if it happened. Of course I hope it doesn't become necessary but you never know what is around the corner. We looked after my mother in law, with help, and I will always be glad we did. She was as happy as she could be, made the most of her ever shrinking world in her own home. It was also very rewarding for me personally, an opportunity to do something to help someone that doesn't often come around. I learned a lot too during that period, missed her terribly when she had gone.