Linux

Ιt depends on your competence. My mom's laptop is Debian with XFCE (2 GB RAM old Chromebook converted to run Debian) and of course, she doesn't use the terminal. But then again, she doesn't even know how to open a new tab on Chrome. She just uses 1 tab at the time (which is why it's enough with 2 GB of RAM). So she's never going to see a terminal in her life, and it's going to work just fine for her, since the only thing she does on a computer is load 1 tab on Chrome, and mostly use Facebook, or youtube, or news/recipe sites that I have put on her bookmark bar. When the computer needs to be updated, I do it for her once a month or so (using the terminal).

But if you're trying to do a lot more than that, then maybe, sometimes, you will need to fix or change things using the terminal.

Package management is probably the biggest thing a Linux user might need to use the terminal for. The graphical package managers used by default on most desktop environments are far too limited.

KDE's Discover for instance is capable of installing (graphical) desktop applications, uninstalling packages and performing updates. Sure, it supports native packages on the majority of distros through PackageKit, as well as Flatpaks and Snaps, but it can only perform very basic package manager operations. I imagine most users will at some point need to install a package that isn't a graphical desktop application, such as a driver or an optional dependency and they will need to use the terminal for it.

To my knowledge, this is also the state of most other graphical package managers that take the form of "software centers" like Discover. More powerful graphical package managers do exist, usually specific to a specific package manager such as Octopi for Pacman. Few distros ship with them, however. I believe one notable exception is OpenSUSE with YaST. There's also dnfdragora on Fedora, which is pretty basic, but might be good enough for most purposes.

My aunt is using Linux without terminal since 2016. Though she at least knows how to open terminal and paste commands when it's necessary (needed a couple of times).