Running poweroff is one of the correct ways on anything Systemd (details). If that doesn’t work then something is broken.

If you haven’t done so already try looking into the journal. sudo journalctl -b -1 -e will take you to the end of the log for the last boot.

GUIs do have advantages in things like discoverability. Honestly the 1983s Apple Lisa nailed this with the idea of having clickable menus annotated with keyboard shortcuts, so users could do the same thing faster next time. For some reason we stopped doing this (especially in web apps), but that’s a reason to make better GUIs, not to RETVRN to the feature set of a VT100.

I don’t know why we have to go on nonsensical diatribes about “UNIX wizards” though when we’re fundamentally talking about a handful of minor UI improvements to things that already exist.