What makes a prohibition genuine
The difference between a real barrier and a convenient obstacle is cost. A convenient obstacle can be removed without permanent loss — it is a misunderstanding waiting to be cleared up, a rule waiting to be waived, a parent waiting to come around. A genuine prohibition protects something real: a family's survival, a person's calling, a community's structure. Breaking it means losing something that cannot simply be recovered. Before your lovers meet, establish exactly what the prohibition protects and who it would harm. The reader needs to feel the weight of it before the desire arrives. Without that weight, the forbidden element is atmosphere, not structure.