My kid (10) got one of my old computers from work. I put linux on it. He doesn't use it a ton, but other than showing him that the windows key opens the menu to search for programs, I've never shown him a single thing.
I think kids aren't the best comparison with senior citizens when it comes to technology. I've got senior citizen parents and I've got nieces and nephews who are all under 10 years old. The kids are so much more adept at pretty much any technology they get their hands on when compared to my parents (iphones, nintendo switch, tv remotes, etc). They start off about as poorly as my parents do but quickly overcome them. My parents aren't tech illiterate, either -- my dad especially was quite a DOS power user back in the day, and to some degree has kept it up with his Windows usage too.
I think part of it might be due to the neural pathways still forming in the kids brains, but I also think a lot of it has to do with who they're around. The kids are around their parents who are using this tech all the time, while my parents don't have that benefit except for in comparatively small doses.
Unironically yes, the most intuitive designs you'll find are on linux.
Keyword: intuitive. This is the problem. People who have seen stuff before have way too much baggage and preconceived notions. People who have used MacOS before, and especially Windows, struggle on linux.
Because linux isn't that. And, heavy on the Windows here. Pretty much every way that Windows does stuff is stupid, unintuitive, and poorly thought out. It is truly the black sheep of Operating Systems. It does stuff different just cuz. Just to fuck with you.
Want to add a ? or a . in a file name? What about name it CON? No. Why not? Fuck you, that's why, this is Windows.
But it's not actually the black sheep, because it's the most popular desktop OS. So people move to Linux or MacOS and they're anticipating Windows weirdness.
Like, they'll open up a web browser and download a random EXE to install a program and then be mad it doesn't work. When the much more obvious thing, opening up a software center and searching for what you want, WOULD work.
Seriously, Windows and MacOS can learn a lot from KDE, Gnome, and their associated applications.