Children have great levels of fluid intelligence, that's how they are able to learn to quickly navigate in a world that they are still very new to. Seniors with decreasing capacity increasingly rely on crystallised intelligence, that's why they can still perform tasks like driving a car but can fail at completely novel tasks, sometimes even using a smartphone if they have not used one before.
It really depends on motivation. My 90 year old grandmother can use a smartphone just fine since she needs it to see pictures of her (great) grandkids.
My late grandma learnt how to use an iPad by herself during her 70s to 80s without any issues, mostly motivated by her wish to read her magazines, doomscroll facebook and play solitaire. Her last job was being a bakery cashier in her 30s and she didn't learn how to use a computer in-between, so there was no skill transfer going on.
Humans and their intelligence are actually incredible and probably will continue to be so, I don't really care what tech/"think" leaders wants us to think.