When my grandmother was in her late 70's, she couldn't figure out the concept of menus on DVDs, so she stuck with VHS well beyond the point others had let it go.

The capabilities of individuals over 70 are hugely varied. Some folks are clear-minded until 100, others start to lose their mental faculties much, much earlier.

I don't think the generation is forgotten, just so vastly different in needs from the core audience that it would require an entirely different solution, and likely an entirely different company model.

I think it's not that they lose their mental faculties... it's that they lived most of their lives in a world without computers (at least home computers - which only became a common occurrence in the 90's, when today's older people were already in their 50's. So they just never learned to use computers and smart phones and are completely unused to their modern UIs. Even I find it hard to use many apps on my phone! Like, how am I supposed to know that wiping carefully up and to the left is the only way to do something!!!??? So, older people may try a few things, and if it's too frustrating they just find something else to do and give up. At least that's my experience with my mom and auntie. Both of them managed only to learn how to open WhatsApp and call family, but it's always an agony when they accidentally touch something and the video disappears, or pauses, or flips so they can see only themselves or some other nonsense. And that's all they use their "smart" phones for! They just wanted an old fashion phone with a big dial buttons, plus a screen to see the person on the other side.

I do wonder how much of that is just convenience, a lot of people just don't want to bother, even if they would figure it out if they tried - they just don't. Your grandmother probably could've figured it out, but tapes were just much more convenient even if you had to rewind them (Obviously there's a learning curve, though)