This situation is slightly different since if you're using it in clamshell mode, you are (I assume) also using an external keyboard. And if you're using the Apple one, then you do have a power button exposed right there.I use my MacBook Air in clamshell mode when working at home. That means the power button isn’t available unless I undock it, open it up, then press the button (if necessary), close it, put it back in the dock, and finally press the touchID button on the keyboard.
Even though this is a much more complicated process than tilting a small computer and pushing a button, I would hardly call it a disaster. It isn’t even inconvenient because it almost never needs to be done.
But I'm gonna keep saying it in my posts so there's no question about how I come down on this issue. Calling this a "disaster" is laughably hyperbolic.