Someone I am in a group with has a husband who was diagnosed with early Alzheimer's, only they have now changed his diagnosis to mild cognitive impairment. She is happy about that. I asked her if she was troubled that the diagnosis doesn't match her experience of all the things her husband can't handle any more. She said no, she is happy because she had originally been told that they might have only two years before he would need more care, and the new diagnosis suggests it could be much longer.
I still feel that if John was 80 I would feel he was doing great, but this isn't what I expected at 63. The doctors seem to think that everything is fine if the John can take care of himself and carry on a conversation without being confused all the time. That is certainly better than the alternative, but not being able to work and share in family organizing make a big difference. John acts older than my father did at 80.