ineptness vs unsuitability

ineptness and unsuitability both are nouns.

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

As nouns, ineptness and unsuitability are synonyms defined as:

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

Other synonyms of ineptness include unsuitableness.

ineptness (noun)	unsuitability (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