obtuseness
/ɒbˈtuː.nɪs.nɪs/Definitions
1. noun
The quality of being obtuse; a lack of sharpness, insight, or discernment.
“She criticized his obtuseness in failing to notice the obvious problem.”
2. noun
A lack of mental acuteness or quickness of understanding.
“His obtuseness made it difficult for him to grasp complex concepts.”