Your logic seems quite sound about why none of the other methods work. But the explicit-consent idea was exactly an attempt to do this! It was the maximum generality that would, hopefully, work despite all the different subcultures.

Except it fell flat in most of them, so far anyway. Hopes were ill-founded.

So what do we do?

People don't want explicit consent, it seems, and also don't want a standard ritual of courting, and so...?

Is there any better idea than trying to promote a culture of a high degree of respect for each other as individuals and hope people work it out on their own?