unsuitability vs ineptness

unsuitability and ineptness both are nouns.

Word	Noun	Adjective	Verb	Adverb
unsuitability	Yes	No	No	No
ineptness	Yes	No	No	No

As nouns, unsuitability and ineptness are synonyms defined as:

unsuitability and ineptness: the quality of having the wrong properties for a specific purpose

Other synonyms of unsuitability include unsuitableness.

unsuitability (noun)	ineptness (noun)
the quality of having the wrong properties for a specific purpose	the quality of having the wrong properties for a specific purpose
	unskillfulness resulting from a lack of training