Not Too BrightOne worth keeping
“Don't hitch a yearlin' to a plow it can't pull.”
California banned child marriage, still legal in 32 states.
In the same vein
All Not Too Bright →Dense. All weight, no sharpness.
Looks alert. Isn't.
Not enough sense in there to do the smallest job.
Can't manage even the simplest task.
Not sharp at all.
He's lost whatever sense he had.