I don't think it's the case in all older people . My DF was in IT at a high level for a very long time (from remembering the days of punched card computers to literally designing high end operating systems ) and he has recently bought himself a raspberry pi for a fun diversion as although hes a complex programmer the Pi's weren't around so he wants to see what's what.
However my DM has been odd. She was perfectly fine with all kinds if technology's and then randomly decided she was too old (her words not mine) and suddenly started exhibiting this almost affected learned helplessness. She apparently suddenly could not work you tube or order anything online
She practically became a stereotype.
Absolutely no indication of dementia , she had been to a memory clinic for a variety of reasons (quite frankly hypochondria for one). We are extremely well placed to identify likely dementia. Not that.
We ensured she was tested for UTI and diabetes. Nope nothing
She honestly seemed to decide one day it was required over the age of 65 to be crap at technology.
It was somewhat muted when we realised it was affected when dsis and I jointly refused to buy into it and pointed out she wouldn't be able to see as many pictures of GC. Amazingly she suddenly decided she could after all figure out (things she had been doing for years).
So who knows , I was surprised at dm suddenly becoming unable to use technology but maybe there is something generational about it being not for them? Who knows ,it certainly was not ability in any way. I guarantee my DF can out switch anyone younger in ability.