<p>Inequalities in social, economic, and political settings play a major role in creating unbalanced scales of opportunities and well-being. One important aspect of inequalities is structural: marginalized groups are pushed to the periphery of the social networks and their access to resources becomes limited. While structural inequalities have been identified in social science literature, the interplay between different factors leading to structural marginalization has not been explored quantitatively in network science. Here, we propose a general network framework that allows taking into account the inequality of opportunities as a group-level fitness function. By tuning group fitness, we show that structural marginalization and rich clubs emerge due to the interplay between group membership preferences and inequalities in fitness. This paper demonstrates quantitatively that to eradicate structural marginalization, it is not enough to increase the minority size or their connectivity; it should be rather centered around strategically providing resources for disadvantaged groups.</p>