Do we really need it?
That's the thing I'm mostly thinking about. Sure,it'll introduce a dark theme but...couldn't a new 'Dark Theme' recolour of the site work just as well?
The current site look is fine. It's not as if it's cumbersome or so bad it needs to be replaced.
Looking at the new design,it's going to be harder for coders to customize.
And making things harder to do is not a good move.