Doesn't gender separation make women feel uncomfortable around men?
Unease between men and women exists in every society, including permissive ones. Separation is not meant to create fear but respect and calm, and it protects the peace of society.
The observation is understandable. Some women seem reserved or tense around men, and one wonders whether the separation of the sexes is the cause. Before drawing a conclusion, though, it is worth looking at both sides.
A permissive society has its tensions too, only in a different form. There one also meets women who are pushy towards men, just as there are men who pressure women. Unease and insecurity, then, do not arise only from separation. They arise just as much when boundaries are missing altogether.
Separation in Islam is not meant to create fear of the other sex. The verses above call on men and women alike to lower their gaze and guard their chastity. This is an attitude of mutual respect. Someone who knows that their boundaries will be respected can meet others with calm and confidence.
Permissiveness, by contrast, harms the peace of many societies. Where there are no boundaries, trust and family life easily come under strain. Anyone who calmly considers the question from every angle will conclude that clear boundaries between men and women do not make people unhealthy. They protect them.