Confidence comes from achievement
"Just be confident bro" is among the most commonly chadsplaining platitudes but also among the most patronizing and illogical. Confidence derives from having achieved something, or having the ability to do things. Confidence can't just be plucked out of thin air. The pharase "just be confident" makes about as much sense as saying "try to be angry" or "pretend you find it funny". Although there are some actors who have the ability create the genuine impression that they are amused or angry, it takes a lot of skill, and usually people can tell if you're fake laughing. Similarly, people will eventually be able to tell that you feigned confidence is staged.
Attractive non-confident men
Furthermore, it disregards the halo effect and failo effect whereby an attractive man's shyness might be regarded as endearing, while an ugly man's confident approach might be interpreted as sexual harassment.