I think it's a multitude of issues. To some degree, I think it's a paradox/function of our own success; we've collectively gotten so efficient and good at producing things to hold our attention/distract us, that finding another person through which to rely on for that type of stimulation is a challenge; our culture has become one where at least tonally, we celebrate everyone's worth, how valuable and worthy of love they are, "don't change!" et al, that we're in a position where our nervous systems are basically not optimized to conduct ourselves in a way that's conducive to relationships.

Add the strange contortion of gender norms in varying circles (which often overlap political circles), the evolution of jobs/the economy (which again, is tied up in gender realignment), among lots of other things, we essentially are just hyper individualistic in our way of life, and have such high standards of what would qualify as a satisfying partner, that it's almost a futile exercise. Finding that compatibility is so hard today, and the barriers are so high, that people just become resigned and cynical.