Ok. Here’s popa’s take. While the “age gap” issue should not be minimized, there are many other issues we can also focus on.
As one wise man once told me: “For purposes of this discussion we will limit ourselves to problems which have solutions.”
There is no solution which will do very much to dent the “age gap” issue. Nobody is going to convince 20 year old girls to not go out, and it really is a bad idea for boys to go out before they are men (or guys). While making it accepted to marry an older girl (woman) is helpful, it will not nearly solve the problem. Besides, I know many older guys; there clearly are other factors involved.
So let’s work on the issues we can solve.
You don’t have to prove Fermat’s last theorem to see this.