If someone (eg your dcs) told you , today, that you have dementia, you'd say, "Don't be so insulting and ridiculous!" I know I would. And that's exactly what most older people say. They hotly deny any decline in capability.
My grandmother is like that - she suffers from Alzheimers and my grandfather has Lewy body dementia - and he is currently "bed blocking" in hospital where he has been since before Christmas because we can't find somewhere to accommodate his needs. He fell in November and as some of the symptoms of his LBD are similar to thise of concussion, they admitted him for observation, but then subsequently decided that it's not safe for him to go home without a comprehensive care plan. However, he and my grandmother need differing levels of care but she is aware enough to refuse live in carers as she doesn't want that kind of invasion of her privacy but not aware enough to understand that my grandfather can't come home without it.
GM just needs carers to pop in twice a day to give her her medication and maybe put a ready meal in the microwave for her, although she complains about them all the time as her Alzheimers has destroyed any brain to mouth filter she had (although it was never the greatest anyway lol). She is still fairly independant though - my uncle takes her shopping every Friday and we have a rota of at least one family member popping in every day to check if she needs any shooping topping up or washing popping in etc, but she can still wash/dress/look after herself. My GF on the other hand now requires 24 hr care as his LBD means he basically has no awareness of what he is doing and is prone to wandering, is doubly incontinent, struggles to communicate and is very prone to falls.
GM refused to accept that their health was failing, and it was a huge struggle to get them to leave the family home in the middle of nowhere that was only accessed by one road that was prone to flooding (we live on the coast) that had become unmanageable. They finally moved into a bungalow nearer us on the mainland and even then my grandmother refused any kind of help, she felt like she could look after my grandfather and got very angry and defensive if we suggested carers or anyone coming in, and she only agreed to carers coming in 3 times a day to give medication because made up some BS story of the doctor needing it "officially recording" that the medications were given, and then she was okay with it.
She'd do things like put clothes in the washer/dryer, switch it on but not start the cycle, so when she came back later on she thought the cycle had finished, take the clothes out and put them away, still unwashed ... but if you tried to point out the fact that things were still marked or stained when she put them back on again, she'd either get angry or upset. She also struggles to understand the time now, so when it gets dark = bedtime, and so with it being dark early, she sometimes goes to bed as early as 5pm as she assumes it's later. It's really hard to watch and as both of her parents are suffering this, and nursing both of her PILs through it my mother has always said that if she ever started showing symptoms of the disease then she'd rather shoot herself than put herself and the rest of the family through the heartache, and I can totally understand her reasoning.