The problem, in my opinion, is the imbalance in self-esteem and self-awareness between the average man and the average woman.
Women, in general, have low self-esteem and rate themselves as less attractive than they really are. The number of stunningly beautiful, intelligent women I know who are obsessively insecure is astounding. Many end up with utter twats who treat them like shit.
Men, on the other hand, tend to be more confident and rate themselves higher in the scale of attractiveness. Completely average, bald 40-somethings with a beer belly truly believe they're God's gift to women and hence they have "the right" to choose a woman of similar attractiveness to what they perceive themselves to be.
This does not only happen to dirty old twats, I have lost count of the number of male friends who are otherwise lovely and would have a great chance with women their own age, but that when looking for a partner focus on women 15 years younger and much more attractive than them... ignoring the evidence that these women mostly look at them as they would at their father, and have a large pool of suitable, younger,m more attractive males around them they will go for.
I am convinced this is the reason OLD apps are chock-a-block full of average looking guys who have been unsuccessful members for years. And still don't learn, or worse, they become bitter because "women are too bloody choosy these days".