lacking in intelligence and ideas
vacuous - empty
The word ‘vacuous’ is a formal way of describing something or somebody stupid and/or meaningless. It is generally used to express disapproval, though something ‘vacuous’ might still be considered fun in a frivolous kind of way in some social contexts. A good way of remembering how to use the term is to think of the similar-looking word ‘vacuum’ which means ‘a place entirely devoid of substance or matter’.
The whole time I was explaining the concept to Tom, he had a vacuous expression on his face. I don't think he understood any of it.
Due to the vacuousness of modern television, I prefer to spend my leisure time reading or exercising, though some people really enjoy that kind of entertainment.
I want somebody qualified and informed to make the presentation, not some lackey just vacuously reeling off facts and figures from a piece of paper.