Methinks you are all missing the point. Suppose I build an aircraft that is electrically powered (motor driving a prop), or hydraulically powered, or compressed air, or human powered. In all cases the prop is a compressor - a device which captures a mass of air and accelerates it aft.
Now if we put a simple turbojet in the plane, it still has to - ahem - capture a mass of air and accelerate it aft. But we have to somehow drive the compressor, and so we have a burner and turbine to recover some of the energy in the airflow to create a continuous Brayton cycle (named after American engineer George Brayton (1830–1892)).