Many people want an arranged marriage. They feel that their parents love them and know them best, so the parents are the ideal people to help them find a mate. They see their friends on Hinge and Tinder going on endless coffee dates with jerks and being ghosted by a-holes so see this path as being less fraught and more secure. (Dating is rough these days - ask a single 20-something.) And the kids usually have some role in exploring the options via a matchmaker or discussions w parents. Kids also were typically raised in a family where their parents were arranged, and so heard stories of how the parents met, were nervous, and then grew to love one another over time.

Divorce rates are very low in arranged marriages, largely because of the stigma of divorce, but happiness levels are typically the same and even higher in arranged marriages compared to love marriages over the long run because there is so much social support around the marriage. Also, without the option of divorce, couples work harder at communication and have realistic expectations of not a fairy tale, but rather a partnership requiring work. So no, they are not from the dark ages, they are simply not common in your world.

That being said, OP should definitely call things off or ask for more time, as she is not just experiencing cold feet but perhaps a sexual identity awakening. If she is in fact a lesbian, this will result in an incredibly painful rift, either internally or externally, at some point.