Not surprising, and not entirely their fault. In my experience, software for operating a scanner or printer is almost invariably terrible. In the case of printers, this is intentional; printers are designed, first and foremost, to extract money from you.

For what it's worth, the Document Scanner app from the Gnome project (the Debian package for it is named simple-scan) is pretty good.

However…

Every morning when he turned it on, he would be greeted by a pop-up from the storage service Dropbox, which he always accepted without reading.

This is not acceptable. If there is a message on your screen, you are expected to read it, so read it. You don't have to re-read it if you see the same message again, but you do have to read it the first time you see it. No excuses. If you get messages that are annoying and unnecessary (note: that's an “and”, not an “or”), then you're using bad software; replace it with something better.

And yes, it's normal to have to replace software with better software. Sturgeon's law is in full force and effect here.

Younger people seem more willing to learn, and can quickly adapt to new skills

Absolutely. The older you get, the harder it is to learn new skills. That's why children are sent to school: they're at exactly the right age to learn all that stuff.

“Gen Z is very comfortable navigating software they’ve never used before, because they’ve been doing it their whole lives,” Bench said.

This is also true of Gen Y (Millennials), including myself, for the same reason.