Ineptitude is the lack of skill — the noun for being inept. You use it of a person (her ineptitude with numbers) or of a group or government (the ineptitude of the response). It is a cool, rather formal word, common in news and complaints when people want to sound serious, not merely rude. In everyday talk, people more often say they were useless or they made a mess of it. Though actually, ineptitude names a pattern, not one slip: one wrong button is a mistake; ineptitude is “they keep showing they cannot do this.”