Have you people never have a grandparent, or a family friend or someone, with dementia? They don't simply go from being OK to shitting their pants and being unable to feed themselves overnight.

Biden is undoubtedly demented. That doesn't mean he is a vegetable (yet). He has cogent periods of time, and those include having slips of the tongue and making other mistakes. And he has impaired periods in which he clearly doesn't even know where he is, can't form coherent sentences and forgets fundamental things.