You are correct, all Stars have a habitable "goldilocks" zone, at least theoretically however, all stars are not created equally. For example, it's possible for an exoplanet to be perfectly situated within a stars goldilocks zone but also be effectively uninhabitable due to any number of factors. One such star related factor that could make the development of life on a planet very difficult if not impossible would be a situation where the exoplanet is in the goldilocks zone but it's host star is far to active in terms of solar flares/radiation and or other sorts of violent disruption that comes from said exoplanet's host star on a frequent basis.