ineptness vs unsuitableness

ineptness and unsuitableness both are nouns.

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

As nouns, ineptness and unsuitableness are synonyms defined as:

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

Other synonyms of ineptness include unsuitability.

ineptness (noun)	unsuitableness (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