In the first place, I agree with Lumifer that in practice people cannot (or will not) return to a previous norm. So any actual way of addressing problems is going to be something different. So I am not "advocating" the old norm in the sense of trying to bring it about. I don't think anyone can do that. But I am suggesting that were it possible, it might be better.

It seems to me certainly true, even if not PC, that one reason that women are more likely to feel bad in the cases under discussion, is that a stable situation is more important to women than to men, so that men are on average more comfortable with casual sex than women are. This is presumably biological: women want help raising their children, while a man in principle will have more children by having as much sex as possible. I think that this has consequences for this discussion.

Let's say some potential sex might turn out to be good or might turn out to be bad. The above reason suggests that outside of marriage it will be more likely to turn out bad from the woman's point of view, than from the man's point of view. It might turn out bad even within marriage, but it would reasonable to think that there will less inequality (in the amount of bad sex from the point of view of each.)

It seems to me possible that the greater equality there might indeed be an adequate reason for preferring the no-sex-before-marriage norm, and the strict consent culture attitudes and arguments are suggestive in this regard. The word "rape" is extremely negative: traditionally people understood it to mean a violent attack on someone. If the word is applied to a situation where consent is imperfect or not completely clear, but in fact there is no such violence or threat of violence, the implication is that the outcome is still extremely bad. I think people would admit, if asked explicitly, that the violent case is worse. But even without the violence, they are saying, it is still very bad.

I am inclined to agree that the situation is very bad: it could cause a woman emotional trauma for a very long time, for example. Compare the good that people get out of non-marital sex: it's pleasant, it can strengthen friendships, and so on. But a single occasion is likely not going to affect your life for months or years. That suggests to me that even a low ratio of the bad cases (admittedly I am talking about cases somewhat lacking in consent) to good cases is not worthwhile: it might be better for women if you simply have no non-marital sex at all.

Of course, as I said, I was talking about cases where there might be some lack in consent. But this might not be the most relevant factor. If you just have "bad sex", even if there is strict consent, the woman may be emotionally affected in very similar ways, as I pointed out above. If we admit that this situation is extremely bad for her, this again might be a reason to prefer to completely avoid non-marital sex, even in comparison with a strict consent culture.