This leads to building a brand of submissive,underconfident,low-impact non- leaders,and hampers their career advancement and growth.我觉得是hampering 这句于与'building a band of .......'是并列关系,要用到hampers这句应该是前面那句的定语从句
另外,在a brand of后面并列了几个词都是形容词,缺少提高名词性成分。