Thank you Ee-chan for the question.
I think other monks have already answered enough about institutional marriage and Shinran Shonin's wife belt.
I think your question is about whether it's OK for a monk to break what the Buddha commanded.
The Buddha certainly said that one should not be attached to the opposite sex.
I think that's because it was thought that in order to attain enlightenment, it was necessary to correct oneself and calm one's mind.
In particular, it can be said that matters relating to sex are representative of what has been commanded.
Unfortunately, our minds get disturbed when we have an obsession with something.
Obsession with the opposite sex seems to be the most important one.
Instead of denying what the Buddha said, if you think about the Buddha's heart, it is important to leave your obsession, and even when it comes to sex, if you don't encounter that target, obsession won't occur. I think that might be it.
In modern society, is it really possible for a man to exist without having any relationship with a woman and a woman if she is a man?
It's safe to say that no one lives under conditions where no obsession with the opposite sex occurs.
Marriage may not resolve all obsessions with the opposite sex, but at least it is possible to move away from quite a few useless obsessions with the opposite sex.
Honen Shonin was recommended to do nembutsu according to his own circumstances, and Shinran Shonin was selected as a carnivorous wife.
I'm sure that wasn't trampling on the Buddha's heart; I think it was an indication that the Buddha's heart was received by illuminating his own body to the fullest extent possible.
I have received the impression that today's monks also have that kind of heart.
I would be happy if it was helpful.