Hi OP, I'm so sorry this is happening. Altzheimers really is so cruel and I really relate to so much of what your saying. My Mum was diagnosed within weeks of my second child being born, he's now 6.
She's still pretty well and has good quality of life (lockdown considered) but just as you say its the sharpness I miss so much. Shes still there but a fuzzier version of herself. I miss the relationship we would have had now if she was well, the insights I would have gained from her, the empathy and humour. Thats not to say she's not kind or funny, she absolutely is but it's not how she was.
Again my mum was desperate to have grand children and while she adores them and spends time with them, she can't do it independently anymore. She stopped working fulltime because she wanted to do more with the kids, a day or two childcare when they were little, incidentally that's when symptoms became more apparent. When we go to the park together if she looses sight of the children for a moment, she panics and is off in all directions looking for them, I'm more worried about loosing than of her than the kids! Her anxiety about loosing stuff and forgetting things makes everything worse for her too.
I really feel for my dad, i think he's depressed and who can blame him, their retirement obviously shot to shit. Again she's pretty well now, but in the nicest way possible, repetitive. He's never been a hugely patient person but he loves my mum but again he must feel the loss of who she was as is partner. Obviously lockdown has made all this so much worse. Video calls just don't work, we decided to make a "childcare" bubble with them autumn last year because I couldn't bear that the kids and she miss out on this time she has.
I know you said you don't want advice, but all I can say is make the most of everything and try not to think about the future to much, it's out of our control. I'm glad you posted. Lots of love to you