You are overthinking this.
At least one generation of today's adults learned how to use a computer when they were little kids, in some areas and income groups, this might be two generations: 36 years (since 1984).
These days elementary school children often use computers for classwork; it isn't brain surgery. Apple computers have been used in schools since the Eighties. The learning curve is blissfully short.
Hell, most kids' first game machine is a smartphone and the kids who turn 18 next year never had lived in a world without iPhones. An iPhone is far more powerful than a Mac SE from the Eighties. A Mac is a computer a first-grader can use.
Basic Mac functions are still pretty much the same as when macOS (then known as OS X) debuted in 2001 or 2002. Again, there are adults who have never lived in a world without macOS.
If you already know how to browse the Internet on your phone or type a basic note/e-mail/message, you can be up and running on a Mac in ninety seconds.
Just buy whatever Mac suits your fancy and budget, the latter which you didn't bother specifying.
That said, I personally wouldn't waste my money on any used/refurbished Mac that is older than the previous model of the currently shipping unit.