Wearinf a hijab is required by a good muslim but a not every hijabi wearer will be a good muslim. Are you trying to use hijab as an excuse to cover up for all their other wrongdoings which go against the Quran? Hijab is a must as is so many other things, maybe a muslim doesn’t wear a hijab but also won’t go around exposing themselves just like a hijabi might do. You’re really getting confused with the fundamentals of being a good/proper Muslim.
Hijab isn’t the only representation of a true muslim, its their goodwill and intention.