Synonyms for Ineptness (same or very similar meaning)
WordNet sense 1 (unskillfulness resulting from a lack of training):
awkwardness, clumsiness, ineptitude, maladroitness, slownessWordNet sense 2 (the quality of having the wrong properties for a specific purpose):
unsuitability, unsuitablenessFrom the ODE community, based on WordNetadd/edit