I thought it was mostly a jamming type effect. The memories are often still here, but become progressively less accessible. They then degrade from lack of use.

It might well be that a lot of memories still exist for longer than it seems. Even if not, stopping the degradation, and allowing new memories to form would allow people to remain cognitive and functional for a LOT longer.

If catched early enough, that could save some memories before they're destroyed

And as the long term effects, at least in mice, look promising, I'm kinda hopeful

Was absolutely awful watching my grandmother decline - and because of that, my mother is horrifically afraid of getting dementia

I hope this can translate from mice to humans fast and we can get something similar.

Restoring destroyed neurons will probably never be possible...
But at least we can stop the decline and new memories can be stored again, and with that a kinda normal life