This is the noun: the state or habit of being shiftless. You use it when you want to name the quality, not the person. If someone’s shiftlessness drives a family mad, it is their lazy, can’t-be-bothered way of living that hurts, not just one lazy afternoon. Same warning as shiftless: it is a hard, old-fashioned word, and it judges character. It is not shiftiness. Shiftiness is a dishonest look; shiftlessness is having no interest in trying.