“While there are definitely great girls out there, and I’m talking generically, as the word “great” is relative, why is there so many problems when these great girls marry?”
If “great” would mean greatness in Middos Tovos and NOT looks, money, successful career, yichus, etc. than that wouldn’t be the case. And just because her friends or neighbors say she has great middos, doesn’t mean much. The ones who really, really know are her immediate family.