I don't know if you understand how recent a phenomenon "romantic relationships" are.
I don't know if you understand how recent a phenomenon your warped ideas about moral conduct are.
A thousand years ago, one of the duties of the Catholic church was to license brothels.
I would take a guess you're thinking "that's not what I meant by romantic relationship", but then the question is what is a romantic relationship?
A relationship based on the ideas of the romantic movement. Specifically, a relationship based on an idea of "true love" that is transcendental, eternal and requires a lifelong commitment expressed through faithful marriage. The kind of love found in fairy tales or at the end of a romance novel. In reality, often believed in very deeply by people who claim that successful marriages resemble friendships.
In a modern sociological context, often contrasted with "confluent" or "liquid" love, increasingly the typical pattern of modern relationships, where love is implicitly understood to be conditional, transactional and based on the meeting of emotional and sexual needs.
And I agree, romantic love sucks. That's why it's dying. It fundamentally doesn't make people happy, which is why half of marriages end in divorce. Because if your spouse can't do anything a friend can't, what's the point in them? Why not just be friends? Why live with the expectation that the only person who can meet your emotional needs also be someone you want to have sex with, much less the
only person you want to have sex with?
And now we have people who imitate the customs of those who would have children in the past without any appreciation that it was never those customs actually bringing people joy.
You're correct that for most of history marriage wasn't arranged on the basis of romantic love.
What you have failed to understand is that this whole idea that marriage should be "joyful" is an idea of romantic love. That's not a thing people ever subscribed to. Noone believed that two people in an arranged marriage would be happy, and there was often little expectation that it would be faithful. Noone believed that sending your 12 year old girl off to marry some 40 year old was going to make her happy. Everyone had a duty to accept their station in life, and often that station really sucked.
If there was a "reward" for any of this, it wasn't some special pleasure that you'd be given in this life as a prize for being such a good boy or girl, but your eventual salvation.
You are a creature born into sin. Your very nature is defiled. You still inexplicably believe this as your ancestors did, and yet you genuinely think something that would have been absolutely ludicrous to them, that your destiny on this earth is to be happy, and that doing what God commands you to do will come with some magic built in reward so you conveniently never to have to face any real struggle or conflict. Moreover, that doing these things will make you the best person and everyone will secretly be really jealous of you (pride is a sin).
That is some romantic bullshit.