idleness vs ineptitude

idleness and ineptitude both are nouns.

Word	Noun	Adjective	Verb	Adverb
idleness	Yes	No	No	No
ineptitude	Yes	No	No	No

As nouns, ineptitude is a hypernym of idleness; that is, ineptitude is a word with a broader meaning than idleness:

Other hypernyms of idleness include worthlessness.

idleness (noun)	ineptitude (noun)
having no employment	having no qualities that would render it valuable or useful
the trait of being idle out of a reluctance to work	unskillfulness resulting from a lack of training
the quality of lacking substance or value