DY:
Absolutely correct. The greatest ingredient in the preparation for marriage is a healthy role model from one’s parents. I wish we all had it. However, among the crowd of younger couples (in older ones, too, but a bit less so), there are many whose role models were either absent or unhealthy. Similarly, the messages from one’s community and culture have a profound effect, and there have been many such messages that are negative.
So the role that chosson and kallah classes play today is far greater than in generations passed. Years ago, nearly all such preparation was done by parents. It is comparatively new that this has become an outsider giving hadracha. But today, the concentration on halacha is still the main focus (no one would minimize its importance), and too little attention is given to the cardinal rules for how to manage relationships. We are all aware of someone whose parental role models were clearly impaired, while they themselves chose to behave very differently. When the entire culture values entitlements, marriage fails to succeed if such attitudes are brought into the home.
Approaching marriage as a sport is a fatal error. How many people seek marriage because their peers are getting married or because they turned that magic age of whatever? These are poor motivators, and they divert the focus to midos that are not conducive to the forming of a shlaimus of a couple.
Yeshivos and schools are notorious for either being obsessed with academic excellence, with midos being nearly ignored. Or the mussar that is promulgated in the yeshiva and school is academic, as opposed to practical. I do believe that yeshivos and Bais Yaakovs could do more here. But these are supplements to a healthy upbringing at home.