Just because someone doesn't understand something that you consider the norm, doesn't make them any less intelligent.
My dad is 80 and is a very good photographer, but i know very little about the tech side of photography and he could wipe the floor with me with his knowledge.
Though I take the OPs statement as one of general knowledge, not specific technical details, so things you just have to be sentient to be aware of.
Like talking to a girl at work (early 20's) and she didn't know where Scotland was....seriously, she didn't know where
****ing Scotland was, she looked at me confused when I was talking about the weather map on the news, and you know, it's the bit on top of England....nope, nothing...
So yes the above is an extreme example, but I come across the same type of thing often and yes OP, it winds me up every time.
Just recently I was talking to someone and mentioned the LHC, Large Hadron Collider, now I don't expect people to know how it works, or even any technical information about what it does.....but really, they had never even heard of it at all...it's not like it's been massive headline news many times over the last few years....
We've bred at least 2 generations without teaching them basic general knowledge.
Additionally, by making almost everything remarkably safe, people can wander around oblivious with the situational awareness of a rock and not die by their hundreds every damn day.
The slippery slope that child-proof medicine and cleaning products bottles have brought us down into the Valley Of The Stupid.
Agreed, apart from the 'teaching them General Knowledge' - it's not taught, it's gained by being sentient, looking at the world around you and not having your nose in Facebook/Social Media 24/7
We really do seem to be socially devolving into the lowest common denominator.