자고로 is used when referring to the tradition, like "as the tradition says / goes". In your example, the speaker is invoking traditional thoughts to justify her own feelings. 너무 완벽해서 내 스타일 아니야 = He is too perfect to suit my taste. 자고로 남자는 좀 진득한 구석이 있어야 매력이지 = As the tradition says, a man should have a persistent/dogged side to be attractive. She's saying she agrees with the traditional thoughts that a man should have a trait of persistence. Note N-이 있어야(지) 매력이다 postulates a condition, that he will be attractive / an attraction only if he has N. It doesn't mean that he already has such a trait.