It’s pretty unreasonable to expect people to know all the intricacies of their OS unless it’s their job, but I do think people could stand to treat their computer less like an unknowable magic box when they need to work with it and take a few minutes to try any basic troubleshooting at all. An example of the sort of thing I’m talking about, last year, my fan stopped working nearly as well and began making crazy amounts of noise. Could I explain to you how the motor in my fan works? Absolutely not. But I unplugged it, looked up how to disassemble it and got out my screwdrivers and opened it up to see if there was anything that I could see wrong with it. Turns out there was a lot of hair wrapped around a shaft and the base of the blades that built up over the years I’ve had it, and removing that and reassembling it was all it took to get it working fine again.
Plenty of people don’t want to put in even that small amount of time and effort to understand things when it comes to computers, which is also a valid choice of its own, but they tend to annoy me when they attribute being unable to do something to the system being too complicated to understand/use, rather than owning their decision to focus their time and energy elsewhere. There are absolutely complex programs that are not accessible for non-tech people on Linux or the BSDs, but the same could be said for Windows and Mac. In the case of the other two, people just choose the option that works for them, but with Linux, they decide ahead of time that Linux is tough and complicated and don’t even try. It could be something as simple as they want to install Debian and need non-free firmware to use their wireless card, there are people who will declare this to complicated to understand and discard the idea of using an OS entirely over a question that can be resolved in less than 5 minutes with a quick search and nano, all because “Oh, I’m not a computer person, it says terminal.”
I think this is the bigger issue, to be honest. Like your example of environmental variables, it’s not a complicated concept, but when a guide says to set the variable for Editor rather than a context menu asking you to choose the default program to open this type of file in the future, all of a sudden, people lose their minds about how complicated it is.
These examples don’t make sense to me as a point against using the terminal, especially since GUI package managers are a thing these days. Many upgrades are under the hood, so to speak, and don’t produce visible changes for most users, and this applies just as much to other operating systems as it does to Linux. When Windows finishes upgrading and reboots, or Chrome tells a user updates are available, and they restart it, how do they know all is good? For the most part, they take it as a given that all is good as long as there’s no new, undesired behavior that starts after the upgrade.
Just because I haven’t been exploited by a security vulnerability or encountered a particular bug is no reason to remain on a version of my OS or programs that is still liable to either of them. That’s just a bizarre argument against staying up to date.