ineptness — without skill or aptitude for a particular task or assignment; maladroit: He is inept at mechanical tasks. She is inept at dealing with people.
ignorance — the state or fact of being ignorant; lack of knowledge, learning, information, etc.
impotence — the condition or quality of being impotent; weakness.
lack — something missing or needed: After he left, they really felt the lack.
stupidity — the state, quality, or fact of being stupid.
weakness — the state or quality of being weak; lack of strength, firmness, vigor, or the like; feebleness.
disinclination — the absence of inclination; reluctance; unwillingness.