appearance is not important maybe

Is it rude to tell someone that they need to improve their appearance? >>> Unless that someone is my family or close friend, I can\'t tell about it because the people\'s respective priorities are different. In someone case, He might think that appearance is not important and there is more important thing(ex) attitude, personality) than appearance. So telling them that they need to improve their appearance makes them feel absurd and rude. But if it is my close friend case, I will tell about it. Although my friend might not want to be judged his appearance, if there is something that can raise his level of appearance( ex) diet, fashion, shaving..) I will tell because I want to make him nice as best friend.