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)

I'm sure you didn't intend to be arrogant and dismissive of my efforts to try to keep her current as time went on.

Yeah I preferred tapes myself rather than deal with the stupid criminal warnings, unskipable content, and often bizarre menu organization on DVDs. Tapes are simple.

One other thing a lot of older people learn is that if they don't want to deal with something they can feign helplessness and someone else will jump in and do it for them.

I clearly remember my grandfather telling me how much it physically hurt to learn a few years before his death. He was highly motivated and figured out a lot on his Android tablet but could only really try to learn for a few minutes every few hours.