For my main point, I suppose I should have specified GNU/Systemd/Linux as needing a CLI, not everything with a Linux kernel. POSIX-style kernel + libc is a very good basis for an OS, and such an OS doesn't need a CLI exposed to the user. It's all the Udev/Systemd/SysVInit & similar stuff that's CLI-only, and desktop Linux tends to require interacting with one or more of those on at least an occasional basis.
There are web based GUIs for systemd (and sysv init too).
But the main reason you don’t see GUIs for those services is because Desktop distros tend to abstract away systemd so you don’t even need to manage it, let alone have a GUI to do so.
Like with Windows, the average user wouldn’t be manually managing what services to start and stop.
And that’s the real crux of things. A lot of the stuff that people say you need a CLI for in Linux are operations that the average user wouldn’t know nor want to do on Windows even with a GUI. They just run a browser and if the machine goes slow they ask someone technical (friend or shop) to fix. I know this because I used to be that friend.
So I really don’t think the CLI is what holds back Linux. It’s just the economics was never there while Microsoft dominated the desktop world. And these days most people use phones and tablets as their general purpose device, so in a way Linux did eventually win anyway.
For my main point, I suppose I should have specified GNU/Systemd/Linux as needing a CLI, not everything with a Linux kernel. POSIX-style kernel + libc is a very good basis for an OS, and such an OS doesn't need a CLI exposed to the user. It's all the Udev/Systemd/SysVInit & similar stuff that's CLI-only, and desktop Linux tends to require interacting with one or more of those on at least an occasional basis.