The problem is:
1) women don't select the "best genes", they select the most handsome guys. Looks don't correlate perfectly with health, strength, intelligence, etc.
2) women are not even reproducing with Chads for the most part in the current state of things. We have the worst system ever, women waste their prime fertility years fucking with contraception and getting abortions, only becoming interested in marriage and kids at the very last minute of their fertility spam. At that point, most can't get Chad to marry them anymore, they marry some old normie betabuxx instead.
Arranged marriage is not perfect, of course, nothing is in this fallen world. But it's the best system possible.