Probably depends on the person. My 79-year-old father has early stages of Alzheimer's/dementia and can't remember the names of his grandkids. I would say that he can't use the internet just fine - even if he wants to.
I had taught my grandma how to use a feature-phone and she was pretty happy with it. Later she was diagnosed with dementia, that phone's battery is dead for some years now.
Somewhere down the line, she forgot how to use her phone (and pretty much anything else). It's sad watching her unlearn things.
at that point, he probably should be considered internet-disabled (among other things)... as an analogy, would you expect a paraplegic to swim with it's own body? sorry, but that's reality...
