I am caregiver for my ex-husband (now partner) with dementia. I got my apartment remodeled, so it would be easier for him with a walk-in shower and seat. He is otherwise healthy, but the shower causes anxiety. After a shower he thanks me and says it feels so good.
There are home care agencies that have Aides who help with just showers, they are highly experienced and know exactly what to do. It might be worth the money not to have a battle each time there is a need for a shower.
It's no different than a child at bath time, I think they would rather run through a sprinkler out in the yard then take a shower :)