Shut down your computer by pressing the physical power button on your computer, that's all it takes.
It should be easy to find in the UI, don't you think? Fundamental features should be easily discoverable. Expecting people to know Ctrl+Alt+Delete to use the latest version of Windows represents major fail.
Having used computers for so long, it would never occur to me that the "Power" button in a "Settings" menu controls the power as opposed to actual "settings" related to power. I wouldn't even look in "Settings" when searching for the power button. So many of these design choices are completely inexplicable.
Log off instead of shutting down? Ctrl-alt-del, then Sign Out. How difficult is that? This is exactly the same as it worked in Windows 7 and XP before that.
Oh, come on. That was one of the things the Start Menu was actually useful for. Most people don't use Ctrl+Alt+Delete.