Consciousness is useful as a concept insofar as it relates to reality. "Consciousness" is a label used to shorthand a complex (and not completely understood) set of phenomena. As a concept, it loses its usefulness as other, more nuanced, better understood concepts replace it (like replacing Newston's gravity with Einstein's relativity) or as the phenomena it describes are shown to be likely false (like the label "phlogiston").

As I am not a student of nueroscience or epistemology, I can't really say in detail whether there is any usefulness in "consciousness" or not. If "consciousness" describes real phenomena, then its usefulness is determined by the understanding of those phenomena and its ability to accurately relate them. If it refers to likely mistaken concepts, then it will be replaced as corrected concepts are formed through study and experiment.In the same way as "that-which-we-call-'phlogiston'" was replaced by a better understanding of thermodynamics.