Marriage also feels complicated when one approaches it through the lens of feminism. Marriage throws in two people and often their families into a system designed to perpetuate patriarchy, subjugate women, and bind men and women (in heteronormative marriage) into strict roles in the marriage.
The point is simple. Intimacy is not about sexuality, penetrative sex, gender, BDSM or any one parameter. Yet, intimacy is about all of them AND MORE.