my FIL died of Parkinson's last month, I don't have experience with the other illnesses listed, but PD is terrible
it first robbed his physical strength and body control, then it robbed his mind. in his lucid moments he prayed for death to come because he hated being a burden on his family. a tough strong guy who did construction and was a probation officer, he was down to 100lbs before he mercifully passed away.
my MIL cared for him for over 10yrs; feeding, bathroom duties, etc. he would see invisible people coming to get them and pull out his guns- luckily he never shot at any of "them". 3 1/2 yrs ago years they moved in with us bc it was too much for just her to handle while caring for their house too.
we had to monitor the doors b/c he would wander off if he could get out and wouldn't be able to tell people who he was or where he lived. the dementia got worse and worse, he didn't know where he was most times and would freak out if my MIL wasn't in sight at all times b/c he at least knew she was his safety line.