I mean, I hate Gnome and I think their work actively harms the Linux ecosystem. Gnome is deliberately unfinished. They have an artistic vision, and that artistic vision is blank uselessness is beautiful. They hate settings, they hate options. They get rid of as many settings and options as they can. Which means their UI feels incomplete to most people who try it for the first time coming from basically anything else. It's so bad that third parties maintain "extensions" to add those options back in, and Gnome does everything they can to break those because their artistic vision does not include options. The ideal Gnome utility is a blank window with a button in the top bar that says "Never Mind."

Many people trying Linux for the first time fail to find a setting in the options menu, conclude that Linux as a whole is dumb and bad and incapable because there's no check box that puts the dock on the side or bottom of the monitor, you tell them to go install GnomeTweaks from the package manager, they point crotchward and say "Install this." And they're right, Gnome is unfinished and it's not the end user's job to finish it for them. Windows 95 had a robust system for changing the system theme, Gnome demanded we stop doing that.

I think you're right in that most Gnome users don't customize the GUI from the terminal, they install extensions. But if you ask a narrow question on a support forum, you'll probably be told to run a terminal command, because that's usually how Linux veterans communicate narrow answers to narrow questions over text-based media, and it's also how a lot of system admin stuff like changing anything that ends up in /etc is done. I've never seen a GUI utility for editing fstab, everyone says to do that in the terminal. Gparted or Gnome-Disk-Utility might do it? I know KDE at least used to have the attitude that admin stuff should be done via the terminal. Dolphin and KATE didn't have the option to Open As Root because they felt if you know enough to mess with the system directly you know enough to use the terminal to do so.

There are also just so many settings that just don't reasonably have a GUI. Give you a personal example, I'm using an old speaker system that has a very hot external amplifier, every time the motherboard's audio circuit would turn on or off the speakers would make a loud pop. I had to edit a couple files to change a 1 to a 0 and a Y to an N to stop that from happening. In Windows that would be a setting buried somewhere in Sound Settings > Volume > Advanced > More Options then the Power Saving tab or something, or maybe a registry key you'd use regedit to change. On Mint I could do it with Nemo and Xed, on some distros you have to use the terminal and something like Nano or Vim to change that setting. And newbies who probably didn't choose their hardware for Linux compatibility and having to do workarounds to compensate are more likely to have to do stuff like that.