You're completely correct about early diagnosis. A family friend who just happened to one of the first specialist dementia nurses in Scotland correctly diagnosed my father early on many years ago. He was prescribed medicine that slows the decline, and while he is not in great shape (he is currently on his hands and knees looking for a pill he dropped) he is in much better shape than my mates mum who was diagnosed years later. She is in a care home and in such a bad shape that her family have stopped visiting her.
I could expand in depth but for now I have to look for a missing pill.