Since it seems that parental choice is dominant in choosing marriage partners in nearly all societies organised on traditional lines:
This suggests that sexual selection operates substantially via parental choice. In other words, sexually selected traits would be expected to have evolved to appeal to parent-in-law primarily - rather than to the prospective sexual partner.
This model seems to account for many of the major trait differences between men and women - and accounts for the poor choices of marriage partner made by so many modern individuals: unaided individual people often make bad partner choices because humans are not 'designed' (by natural selection) to choose their own marriage partners.
(i.e. People make bad choices because they lack the instincts to make good ones.)
Indeed, the model may also explain the nature of the bad choices typically made.
Parental choice would be expected to give most weight to 'sensible' criteria such as a man's economic prospects, a woman's youth and health, family background and so forth; but would tend relatively to neglect individual, personal qualities such as being charming, good-looking, sexy and fun-to-be-with.
Parental choice alone would often lead to dull spouses.
In a system of parental choice - where all individual choices of spouse operate withing a 'field' of pre-approved candidates; it might therefore be expected that the individual woman and man would tend to focus on exactly these compensatory aspects. In other words, individual choice would tend to pick the most charming, good-looking, sexy and fun of the possible, parentally-chosen, candidates.
This would work pretty well, with the parents choosing potential spouses of solid, grand-children-rearing quality; and the individual husband and wife being able to pick the one who is most enjoyable to be with.
But take away the framework of parental choice, as we have in the modern West, and leave choice purely to individuals and you get... well, exactly the kind of sexual choices which people make in the modern West; where they go for the most charming, good-looking, sexy and fun-to-be-with of available people, regardless of who is a sensible, solid choice of child-rearing partner.