It's annoying, but I hope people don't go around shouting at people.
My mum has dementia and you'd never think it. It's confusing for her to get the mask on with her glasses, but she tries.
Visual perception is also affected with dementia, made worse by wearing a mask. She often ends up with it only over her mouth, and I'm not going to add to her confusion by insisting. She's trying, which is more than a lot of people.
I'd have plenty to say if someone shouted at her!