dumb and slow to understand
obtuse - dull
Somebody regarded as being ‘obtuse’ is considered to be dim-witted and slow on the uptake. It’s important to note that this word does not exclusively mean that a person lacks the sharpness or intellect to comprehend something. It can also mean that they deliberately pretend to be this way in order to be difficult. The term is always used in a negative context.
Don’t be obtuse. You know exactly what I’m getting at but you’re pretending not to just to provoke a reaction from me.
Our manager’s decision making during the project displayed a naivety bordering on obtuseness.
Jim thinks he did nothing wrong. Perhaps he’s too obtuse to grasp just how much damage his actions caused to the company.